i have the procar rally 1000 seats in my 72 firebird, they are a full size seat & would fit great in an bigger A body car too. very firm & supportive with the side bolsters but also incredibly comfortable. & they have fully reclining backs & adjustable headrests. they come in different colors & even real leather & make a low back option too. & very good price at about $325ea when i got them & now about $340ea at amazon, other places liek summit are more expensive but amazon has the best prices.
they also come with standard seat tracks that can be made to use in most cars or they sell more vehicle specific tracks. i chose to make some custom plates to bolt to the seat & allow me to use the stock firebird tracks, they sit a little lower than the tracks procar sells for more head clearance. been 5 years since installed & they hold up great & im still very happy with them. they also match the rear seat & door panel vertical stitching for a close to stock look.
https://www.summitracing.com/search/brand/procar