RHS or EDDY

I really dont think he'll have a problem with the J heads cracking.

Since he all ready has them in use, he'll just need to put the same head back on the smae bank it came off of. Unless the heads have worn since it was rebuilt, then new guides wont be needed. But we'll assume this needs to be done. Just as a worst case and hope for better.
Same deal withthe valve seats. There less likely to have been worn out. Since he has the heads, it should work out cheaper. The big question is, what they flow now and what he can use in terms of cfm in the heads.