When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Easiest; get the 78 seats. Me, I found a set of C5 seats for 275, pulled and sold the slides, measured and drilled the C5 aluminum seat frame and mounted my 78 slides. I had to put a small spacer in front and back to allow the seat slide mechanism to work. Make a template from cardboard from the bottom of the 78's seat bolt pattern and go.
I took the easy way... Took my seats to a upholstery shop....They repaired,welded,cleaned and painted the frame and slides.. Then started building up the padding... adding hip,thigh and under knee bolsters...and perforated center panel... Never got uncomfortable or sweaty on the 2400 mile Power Tour this June...
I have a pair of seats from a 76 for sale. If not interested, my recommendation would be to go with seats from a Fiero. If you are not familiar, google will bring up plenty of information.