I cracked a piston

yes if they are 87 then they are forged, but I would be cautous of using a "used" piston, you may need a bore, and that will make the pistons useless. That and stock forged pistons are heavy. I had a bud that tried to cut a corner and bought a used set of pistons (Ross) and ended up tearing it back apart.

Its a good idea but for the work and all I would save and do it right the first time.
 
i agree, break down and buy some new pistons it's better than having another piston break and wiping out a lower end or worse haveing a rod sent through the side of your block. Je makes some nice pistons and they are reasonably priced.