Hi
there are different ways of identifying what engine you have. Probsbly the best way is to get a casting number off of the block and go to one of the number identification sites.
If you are going to rebuild the carberator, look for a number stamped on the bowel of the carberator. It should have at least 5 numbers or more on it. If you take this to the parts store , they should be able to identify what carberator you have and get the right kit for you.
Good luck
Jim