So, in doing some reading about the Apollo program, and the Saturn V in particular, I started to wonder where NASA could have gone with the program had they been allowed to further develop it. IOTL, they weren't allowed to because of budget cuts from Vietnam. There were proposals however for uprated F-1 and J-2 engines to increase the Saturn V's payload to Low Earth Orbit to 150 tons. So, my question is, with no US involvement in Vietnam, how much further would NASA develop the Saturn V and how long would it keep flying? Bonus points if you can keep Apollo going with it and work in additional moon landings and/or a push for Mars.