replacement seat suggestions

You don't specifically say it, but your comments infer that you are a tall driver. Virtually any aftermarket seat will have a thicker seat and back, both of which will cramp a taller driver. Recaros are the worst from this standpoint. Two possibilities: late Corvette seats are quite nice, and re-padded, reupholstered stock seats work well. I am 6'2" and using redone early stock seats, I can comfortably drive our '72 for 10 hours without strain, or open-track while wearing a helmet, and with a reworked rt-side firewall, I can do the same from the passenger seat while my 5'4" wife drives. Cost is roughly the same and you KNOW they'll fit.