Welcome, nice score for $300.00!
If it is in fact a 73, it would probably not have been a 340 car. There were a small number of them sold through 3 dealerships in Western Canada in 71 and 72, not sure the exact number but it wasn't a lot. Sixth digit of the vin is the year, next one is assembly plant. An R in the 7th spot means Windsor Ontario assembly plant. If born with a 318/904 it will almost guaranteed have a 7.25 inch rear end. Lots of suggestions for a build have been mentioned, good luck with your plans, keep us posted.
