[BilLster]

first off lets get the basic's and asume that the crank is ok.

where did you get the pistons from ? did you already have them or where did you by them from somewhere else ?

This is in what year 351 block ?

you can get a strocker crank that workswith 351 rods and 302 pistons the 302 pistons have smaller hight and ring package thats what makes it work.?

if everything is as it should be and there still is interference get the dremel out for all 8 pistons but that would be a last resorte.