meet ginger
The 7 1/4 should be fine if your just going to drop in the motor. If you plan on rebuilding it first then it all will depend on how hard you beat it. I had a 72 dart with a 318 904 and a 7 1/4 beat it until I threw a rod then droped in a 360 that someone suposidly rebuilt and beat the snot out of it....It wasnt until I rebuilt the 360 and did it correct that I started to have problems with the rear nothing major just when I hot rodded it the spider gears couldnt hold it. I replaced the spider gears 3 times until I bought an 8 3/4.... back then I scored my 8 3/4 for $300 and it was narrowed a couple inches narrower than stock. now i dont want to guess what a complete 8 3/4 would go for.