A frankly better scenario would have been to restart Apollo CSM production. Use Saturn 1B as a launcher. Skylab had provisions for two or three long duration mission, or half a dozen short ones. A backup also existed.
That could have been used till the early 1980’s when a better and more realistic shuttle comes on line.
This does butterfly away female astronauts until the mid 80’s.
Restarting ANY production lines for Apollo, including the Saturn 1B and CM, was going to be massively expensive. Doable mind you but probably more than Congress was willing to pony up and NASA, rightly or wrongly had already hung it's hat on the Integrated Program Plan/Space Transportation System (https://en.wikipedia.org/wiki/Space_Transportation_System) of which the Shuttle was the only survivor. And once the restart was done the operating costs were going to be high using legacy Apollo hardware as well. It's not really likely that Congress would have authorized the funds needed to launch Skylab II and somewhere around my forums I just saw a NASA report on the last Saturn V which basically said if they didn't use it by about 1975 or so nothing short of a complete rebuild was going to getting it flying. And if you thought the cost for restarting things for Saturn 1B were crazy...
(And maybe not on the women astronauts since the same social pressures are there and even if the CM never seats more than three one can still be made available)
And then there's the idea of a "better and more realistic shuttle' itself since if you've seen how the Shuttle became what it was you should be very aware that the overall goal wasn't likely to aim that low even if forced to do so
The Space Transportation System, (note this being the official "program name" of the Shuttle for a reason) was always going to be the 'foot-in-the-door' to a future IPP if NASA had anything to say about it. And in that same mindset a return to "normal" with Apollo level funding and support was just around the corner, any day now once everyone comes to their senses and restores NASA and manned spaceflight to the highest priority level. Not. Going. To. Happen.
Most of my alt-TL notes avoid this by avoiding the Lunar goal by various means the only one that does has someone going back in time with enough evidence to convince NASA management that YES they mean to cut your budget and make you JUST a regular part of the government to get ready or suffer. (And in most cases of the latter I examine the personalities in general and it's not a pretty ending)
Now lets actually assume they get this and manage to fund Skylab II into space. Note I'm not mocking or disparaging the concept I just want to make sure we're all on the same page from the get-go.
Why would we assume that a "better and more realistic shuttle" would ever come about? The Soviets only built Buran because the US was building the Shuttle. Originally they, and the US wanted something smaller that could launch on an existing ELV. (Both were essentially more like the Dynasoar than our Shuttle)
While cheaper to develop and deploy than a 'full-size' shuttle the problem was it didn't really allow much else having somewhat less 'capability' than Soyuz or Apollo and costing far more to put into and use in service. (Seriously, the costs for making the Apollo CM both reusable and refurbishment costs were pretty well defined and further making it capable of hauling up to 5 astronauts was pretty straight forward while recovery costs would come down as the needed sea support was actually lower than Apollo used by quite a bit. Soyuz on the other hand was pretty much at its limits so going with a mini-shuttle might have been a better option, but again the costs were a big issue for all involved) And the "big" deal to the Powers-That-Be was that neither option would save that much money or give that much more capability than just continuing to use Apollo/Soyuz into the future since there was not very much PLANNED or SUPPORTED to do in space. Really bigger space stations through the 80s and 90s is about it and in the case of the US there is active opposition to going back to the Moon or on to Mars and the Soviets simply can't afford to do so.
Keep in mind that despite using 'known' technology there's no budget or support for expanded activities because Congress if it wants, (and most wanted to, especially in manned space) they now can cut MORE rather than less. NASA had plans of course, (so did the Soviet rocket program) but not the funding and support to carry them through. Also keep in mind the production line was shut down in 1968 if nothing changes and by 1972 they were mostly scrapped. Note that the DECSION to stop production was being discussed as early as 1965 but the actual shutdown and aim more for a 'shuttle' came just before Apollo 11 landed. (Some documents here: https://history.nasa.gov/SP-4407/vol4/cover.pdf, specifically I-46, interesting discussions here; https://forum.nasaspaceflight.com/index.php?topic=43467.0, and here; https://forum.nasaspaceflight.com/index.php?topic=26667.0 among others) The only legacy item of Apollo to continue through 1972 was standby production of the J2 as it was considered a possible space shuttle engine until the mid-70s.
So what we'd have in most cases is the US still flying "Apollo-like" CM's launched on upgraded, (modernized not really more capable but things like electronic and materials upgrades and the H1 going to the RS-27 and such) Saturn-1Bs and the Russians flying upgraded Soyuz's on R7's. Arguably you could get things to where we are now pretty easy over the same period. ISS segments go up on Saturn-1B's and Proton's instead of the Shuttle but now you have to have dedicated US crew flights added in. Ok. Having the Saturn-1B available for some missions might help somewhat as it would be unlikely that NASA would be using any Titan's and there would be no Titan-IV but possibly some different models of the Titan-IIIE/M so you might see some allowed 'growth' in both Viking and Voyager. (Bill, like most in Congress were more favorable towards unmanned missions as they cost less but pretty much all of them IIRC had "issues" with the original "Grand Tour" and Voyager Mars plans due to cost)
In general I like the idea if you can get it to fly past the NASA-that-was and Congress. The former is actually harder than the latter since you have to get them to admit and face the fact that "Apollo" was a one-of and is not coming back which to my mind would have been a VERY valuable lesson for them to learn 40 years ago. Von Braun IIRC correctly remarked (paraphrasing) that working on a shoe string was actually more conducive to innovation and out-of-the-box thinking than having unlimited support and funding because you really had to prioritize and plan your work around what you had not necessarily what you really wanted.
But NASA was an organization and culture that had gone from less than 15 minutes of "space" experience when it got the call to the surface of the Moon in less than 8 years and any "lesser" challenge was seen as an insult. On the gripping hand that 'miracle' came from a heavy national commitment and support that really started to fade almost as soon as it was begun and a big problem was that organization and culture couldn't transition well if at all to the lesser challenges and frankly no one wanted to really try at the time. (Hence why I see "here's proof of the future" turning out badly)
Randy