Just for grins I weighed a stock E9 seat yesterday (missing a lot of horsehair and leather) and the cheesy bathroom scale said almost 60#s. I'm not sure what a "heavy" seat is if the stockers are at 60#s. My race seat weighs 29#s.not sure that new style seats will fit as most of them have adjustable bases which are taller ... the e9 has raised bases as part of the car. and @craterface is correct, they are very heavy. i would try to borrow a seat from somebody in socal ... especially if somebody is repainting their car and has the seats out for a while.
As Scott (edit: I originally wrote Gary... Ooops, my apologies) said most of the 80’s and newer Bmw seats have completely different mounting position and philosophy. While it is possible to “make them work” in the e9, if it is for a temporary assignment, it is definitely not worth the time and re engineering required.not sure that new style seats will fit as most of them have adjustable bases which are taller ... the e9 has raised bases as part of the car.
Trade you for the "no sunroof."Andy, I am 6'5" with no sunroof but I raised the front of the seats 3/8" or so using drill bushings/shims between seat and seat rail and used longer M6 bolts, this gives more support for my 36" inseam legs. Made a big difference for me.