The RN was the first customer for the Phantom and it placed its order in 1965 for delivery from 1967, the delay I assume being for the development of mod specific to Britain. For Canada to get aircraft in 1965 they'd have to order in about 1963 and then compete with US and UK production in the years when McD was producing and average of 63 a month and peaking at 72 a month to re-equip US units fighting in Vietnam.
If Canada was to be the first export customer for the Phantom it would be offered the F4C, but then in later batches this version would be out of production so Canada would have to buy whatever was the latest production version. Thus Canada would end up with a couple of 'orphan' fleets of small numbers of aircraft and have to work something out about harmonising these fleets as much as possible, all of which drives up costs.
Also most armed forces compromise between platform numbers and available budget, so I seriously doubt Canada is getting the same numbers of Phantoms as it got F101, F104 and F5, particularly given the complex and convoluted method of the F101 buys and how it was tied to the BOMARC. That said if the RCAF got the Phantom it wouldn't need the same number of aircraft due to the Phantoms greater capability.
All very true. Probably what one's looking at is that (1) the buy takes until a little later, probably right at the end of the Pearson years and because he was farthest right (out of his grab-bag of political positions) on fiscal policy especially during fits of pique Trudeau would like to cancel the contract, but too many people in the party, American pressure, and possibly some kind of industrial workshare where Canadair puts in the Speys (
les plus porc des porcs for Quebec right at the height of the separatist movement) means that the project follows through. This could have additional ripple effects through defense (sorry, defence

procurement, like with the
Iroquois-class build or with getting and keeping any parts of the Army (Land or Mobile Command at the time? I forget the terminology of that whole clustershag) mechanized other than 4 CMBG. But the buy goes ahead, and really it comes in the very start of the Seventies (like beginnings of delivery in 1970 or so) and it's the -E line, maximal Phantom capability, which Canada gets. (To the OP, those images in the first post are just gorgeous, pure hardware porn

) That does indeed mean a reduction in numbers, probably something on the lines of:
- Ten front-line squadrons of 12 each, with four for 1st Air Division at Solingen, West Germany where they can share a common maintenance and parts pool potentially with the USAF and Luftwaffe, and three each basically pointed east and west within home air defense
- One, possibly 16-jet squadron for training and weapons-integration testing
- A decent number of spares, 34 would be the equivalent of 25% of the in-service fleet and probably a maximal result on that based on what HMCG is willing to lay out
So that's a total of 170 airframes for the fleet, all F-4Es, with an emphasis on ground-attack capabilities for 1st Air Division and emphasis on long-haul AAM trucking for the home-based aircraft. Sounds like an entirely plausible outcome.
And again, with the general parsimoniousness of the Defence budget and the fact that there were some pretty decent upgrades available for Phantoms going on into the Eighties (particularly if you tried to draft the coattails of the Germans, Israelis, or South Koreans to keep per-unit prices down) the airframes probably soldier on into the mid-Nineties, with duty in the Gulf and Bosnia starting to show their age, on the lines of "they're rugged, outstanding bomb trucks when you have total air superiority, but the airframes themselves are wearing thin." That pushes you on past the Mulroney window of opportunity (if Joe Clark had gotten a majority I'd have said that for Canada IOTL
sans this Phantom purchase, what made the most sense was not trying to have champagne on a beer budget with -15s or -18s when you were still competing for slots with the USN/USMC and paying development costs, but by getting in on the great F-16 license-build fire sale and getting the -16s assembled by Canadair in the bargain, more bribing
La Belle Provence with defense contracts) this puts you in the middle and later Nineties with a beloved but shagged-out fleet in need of replacement. At that point you can either get in on however the Eurofighter project is going or, given that this is exactly the wrong moment to try and get in line for Superbugs, all of a sudden the Gripen starts to look a lot more attractive. You can probably get more of them, and in multi-role configuration rather than the "Tranche 1" Typhoons which were pretty much pure interceptors/dogfighters with hefty bills for upgrades later, and since Saab can only churn out so many at once you can probably, again, get a workshare agreement up and running where Saab builds the key components and assembly, particularly if you want to steal a march on the Gripen-NG with an early engine upgrade, by Bombardier. In that case you're probably comfortably home to at least six squadrons and maybe, just maybe, as many as eight. But definitely six plus the OCU/Eval unit, probably at least 110 airframes, up to 120 if they're lucky which would be quite a decent haul (on the principle of a minimum of four squadrons at all times for home air defense, and a maximum capacity to surge two squadrons simultaneously for short- to medium-term overseas operations.)
As I said in passing above, one of the interesting things is, what does this mean for other defense procurement choices? Spending the very end of the Sixties and most of the first half of the Seventies paying off acquisition of the all-Phantom fleet and affiliated weapons systems is going to have a real effect on both shipbuilding and on the army. The famed and key AVGP purchases (Cougar and Bison and the rest) might not happen because in stagflated times the Trudeau government would argue the cupboard was bare, and that home forces would just have to make do in the name of keeping 4 CMBG in shape (although that might have some side benefits for 4 CMBG since it's a small-batch procurement project, perhaps more ATGM bulk purchases and maybe late-model Chieftains with Stillbrew armor instead of Leo 1s for the cavalry regiment in residence just to show Land Command wasn't being abandoned totally because of shiny jets.)