71-72 rear spring hangers on 69 frame

[Drewbee]

Looking for some help. I have a 69 k10 frame that I received cheap to transfer my 2wd over. Basically just pulling the body of the 2wd off and putting it on the 4wd frame. My problem is that the 69 frame had the spring hangers removed. The front spring hangers were the same as all other 67-72 trucks I believe but the issue is the rear spring hangers. In 69 the front rear spring hangers were shorter. People say just use the71-72 hangers, which is great however they're longer and I'm trying to figure out the correct way to measure and put them on. I'm trying to make sure all my measurements and angles correct the first time. Does anyone with more knowledge of this that can help?