I have an 87 GTA. The seat upholstery is in perfect condition, but the seat foam could be replaced. Am I reading correctly that replacement foam for the GTA is unobtainium?

 

What's the matter with the foam? If the upholstery is perfect how does the foam get pooched? Foam is obtainable, you might have to spend time looking, but it's there. If yours is just cracked or hollowed, it can be repaired, but again, you have to spend time looking for an experienced upholsterer.

 

The seat foam is 32 years old and so it's not quite as robust as it was new.
I was hoping I could find a supplier that sells a brand new replacement.

 

You can use a steam machine on the foam, The steam will expand the foam back to it's original shape and thickness.

 

Yes, steam. But if it won't come back, or won't stay, a good shop can hand cut and layer new foam on top of the factory piece. This needs to be done sometimes with new covers, to make them fit tight and not be baggy or loose.

 

I had this issue and an upholstery shop lined the original foam with a thin sheet of foam to give it more volume. Looked great after that.