WIW corvette old fuelie exhaust manifolds
 

I hate asking, but I have googled to find a value, and cant find anything, and don't want to join a corvette forum to find out. Probably should, but for now asking here first.
I have 58-61 vintage exhaust manifolds that are unique to the 290-315HP 283s and a guy wants them. I just dont know what to ask.

Any corvette guys know?