Mine is a '77 - the seat back is fixed at around 15* , and that doesn't work at all for me . I did move it back and raised it up some and changed the angle a bit . I need to sit vertical with the back and 8-10* positive on the seat bottom to be halfway comfortable . I'm 6' w/30" waist and pretty light - it's tough to find cushion material that isn't rock hard due to my weight (155) . I have considered removing the side frames and re-locating the pins where the seat back locks in - but that might detract the value of a nicely recovered stock seat . Not sure what the PO paid to have them done , but someone really did a nice job . I'll have to get some pics if it ever stops raining here ....
Sarge
Sarge