I put some pro comp super seats intended for a J@@p in my 79. They bolted right to the stock tracks. In each corner there was 3 holes, 2 threaded and one not. They bolted right into the non-threaded holes. But this is on a 79, which is different from earlier trucks, and i think they changed seats again in 81.
In my 40 I've got Bestop J**p replacement seats which I mounted to salvage Suburban sliders which required a small amount of modification. A significant improvement in ride quality.
In my 60 (pictured) I've got salvage Camry electric, leather seats with lumbar. I had to fab brackets to be able to mount them, but it wasn't too hard. A huge improvement in ride quality.
on the old ricebox, the supra seats were mounted to the oem bench frame with flat stock. the saturn seats are just sitting loosely in the back of the 65 and the pulsar seats mount off my rollcage. nothing is/was sitting on oem mounts