My pops threw some Honda Accord seats in the 83 Brat, there's still a decent amount of headroom. I've got some 90s Impreza seats in my 79 GL wagon, and I still fit in there (being about 6'1") Just adapted the stock rails with some 1/8" ot 1/4" steel bar. My 87 wagon has XT seats in it, which the wife says are too hard. I don't think they're that bad, but they are a bit thinner and sit lower, and have the adjusty thingy so you can change the height if you need. My favorite seat swap is the cheap O'Reilly's racing seats we put in my buddies beater 90s impreza wagon. Tons of bolstering, and more comfortable than the stock STi seats by far. They cost like $160 new.
I'd recommend a trip to a local boneyard to find some seats you like, then just adapt the existing rails from your seats to fit the ones you bring home. Just be careful getting power seats, as the mounts for those can be very weird and difficult to adapt.
