It is not going to matter what block you put in, because they are essentially all the same. The reason some were sslower than others would be due to weight of vehicle, the whole s.d. vs. mass air deal, and stock intake, exaust... I would get an 87-92 for the forged internals, and thats about all I would worry about. All of these engines were virtually the same horsepower. Dont worry about it, if he's got a '94 on hand get it, if not go with an 87-92.