what is the biggest engine I can drop into a 77 pinto without having to make changes to the suspension

 

Probably a 289 would be my guess.

 

the 302 came in the pinto wagon for a few years. don't remember which years..
it came with stiffer springs, shocks and a huge front sway bar and a standard sway bar in the rear. most coupes and runabouts didn't come with a rear sway bar.. so find out which years came with the v-8 in the wagons. and the v-8 will fit in the same year hatch backs and coupes... the sway bars may be challenging to find... if I remember the first gen ranger springs will fit and are stiffer than the stock pinto springs... double check the diameter and length...