68 valiant signet seat foam

So I'm having my low back bucket seats redone locally and the upholster called me last night to tell me the foam was shot. Said it would cost another $200 for him to make them unless I can find them for cheaper. Well I can't find the right ones and the ones I did find are around $240. 67 mustang ones look close for $100 a pair shipped. He said we might be able to modify them to work. Anyone have a better solution?