Mark,
OK, take out 302 and insert a Rover V8 then or a Ford 2.3 - 4 cyl. or "insert cheap internal combustion engine of choice here". The idea is the same. If you want to kill 2 birds (the kinds with wings, not Bristols) with one stone, find a car that you wouldn't mind driving with a bad engine and a very low cost. Maybe something like this £212.00 Spartan on eBay:
Rebuild its motor and have good cheap transportation in addition to a great learning experience. Maybe you can drive if for a bit and then sell it for £700 and buy something a little nicer and do it again. Perhaps you would work your way up to a GT40 before you know it. The point is, don't sit around and dream of the day. I started looking at mid-engine V8 powered cars in 1969 and didn't buy one until 2000. Such is life. So, you can't afford a GT40 now, well get yourself ready for the day when you can! "Every journey starts with the first step," so the old adage says. Well, several of us have tried to give you some good first steps. Only time will tell where you end up. But, again, good luck.