look at a mid 70 into the 80's mid GM size cars, you will have to redo the kick out on the side of the frame BUT ya wont have to worry about the kick-UP of the frame in the rear.
BUT if he just has to use a S10 frame ya want a 2wheel drive one, OR the front frame section from a 2000 or newer 2wheeldrive Blazer that way you can upgrade the front rotors to a much larger size if ya want to by using late model Camaro (like a 2000 model) hubs & rotors.