My 62 Valiant

valiant62 said
I was also considering maybe putting a 318 or something in it.

It's been done, but it is costly and difficult to do a quality job of it. The engine bay is super tight on the '60-'62 A-bodies, you will lose your heater, etc.

Would you know how much it would be to get one of those seats re-done? just kinda wondering..

It's costly to have a good, craftsmanlike job done by a professional with nice materials. See here.

You may want to look at scoring some seats from a first-generation Sebring convertible. They have built-in 3-point seat belts.