Ok i think i found the difference.

oh yeah the reson for the differnt crank and pston is this. the pin hieght on the 87 piston is different then teh later models and that in turn uses a little bit longer rod on the 87 also

Carl could tell us how accurate that is. It would seem like that if that were the case then an 88+ cylinder on to an 87 bottom end wouldnt be a direct bolt on swap right? I'm telling you, there cant be any huge differences in the pistons because of the fact that the cylinders just swap back and forth.