main differences between 73-79, 81-87

[Honest Bob]

Here is what I have learned from putting a 2wd 75 body on an 84 4x4 frame, parting out some of the 73-80 trucks and owning an 84 M1009 CUCV.

1) The very front section of the frames where the bumper mounts are different.
2) I had to drill new holes in the 84 frame to mount the 75 box for the second set of bed bolts from the cab (Never seen this mentioned anywhere!).
3) Dash pads are different.
4) body mounts are different you need to use the ones for the year of your frame.
5) 81+ had thinner glass.
6) Tailgate mounting hardware is different.
7) Gauge cluster wiring dont seem to standardize until 76-77?. 73-75 have an amp meter instead of voltage meter and trying to use different year gauges without redoing the wiring can result in burning wires.
8) Power steering boxes, hoses, and hydroboost units - 73-80 have SAE fittings and 81+ have metric fittings.
9) Windshield washer pumps on the early trucks are built into the wiper motor.
10) Windshield washer buttons are on the dash instead of on the column.
11) High beam switch on the floor until?
12) Steering columns between 73-80 and 81+ use a different spline or D shape (I forget the exact difference but the popular xj shaft mod isnt as bolt on on the earlier trucks as the later ones.
13) Ebrake setups are completely different including the backing plates on the FF 14bolt (not sure about other axles).
14) 73-? use glass fuses instead of the blade type in the fuse boxes.
15) The np205 mount rod between the trans and transfercase stopped being used at some point?

I have friends with 81+ trucks and everytime I think "I have one of those!" the 73-80 stuff I have doesnt fit the 81+. Basically assume the 73-80 parts wont fit the 81-87 and visa versa, they are as different as a similar truck can be. Compatibility does seem to increase with every year but the 73-75 (maybe 76?) trucks are headaches as far as compatibility with the older years.