1963 K10 Axle Swap - When did the rear perch width get wider?

[BFD305]

Hello All - Well I ventured out and picked up a '63 K10. Excited to get started. It is disassembled right now, so I figure its a good time to swap out the closed knuckle front and get some disc brakes too.

I found both front and rear assemblies from a '72 K10. I know the front will just bolt on, but not sure on the back.

What year did the spring perches get wider?

I have searched but have not gotten a definitive answer. Not a lot on these 60-66 K10's.

Thanks!

[Mike C]

1/2 and 3/4 tons got wider in '73. Compared to the 69-72 trucks. I THINK 67-68 same spring perch width but they have unique springs.

I know zip about trucks earlier than that.

One ton 4x4's kept the same narrow spring perch spacing as the 67-72 trucks through the end of the square bodies.

[FLATFENDER54]

I just bolted in a 1973 k20, 8 lug, 14bolt into my 62 k10 frame with zero mods needed. I was expecting it to need the perches moved and was surprised when it didnt need it. I had to get a. 73-87 extended rear brake line for a 6 inch lift to reach the brake line on the frame. These old trucks sit high.

The matching 73 front dana 44 needed just a little modification but it fit