Stock suspension racers

Just had to do some reading on 8 1/4 read ends real quick. Since my car was originally a 318 car I was kinda thinking it might have an 8 1/4 already I always just assumed it was 7 1/4 hardly ever hear of 8 1/4s I think anyway. I'm gonna have to check when I get home today. Not a big fan of running ford or Chevy parts.