Hey, check out wikipedia.org and search for "ford bellhousing bolt pattern." It will come up with a page that lists which engines work with which bolt patterns.
From that, find an engine that has a good hp/weight ratio. Weight is one of the most imporant things on a buggy due to the way they're configured.
Just make sure you check out the weight on engines and not just hp!
Original pinto engines are heavier than some newer v6's!
Just do your research.
If you're interested in using a Ford V6, the Duratec 30 or 35 are great choices. The 3.0 is over 200 hp/tq and under 400 lb. (all aluminum block and heads).
PM me your email and I can send you a list of engine weights that I found on the net, if you'd like.
Pat