[rs74]

Originally Posted by JJorgensen52

I will answer as best I can, I've been away from the board with the holidays and call.

As far as I was able to tell, the late square body (mine was an '87) had a taller frame section in the center under the cab. I do think the '72 frame was a bit thicker, though. Either way, both trucks had a similar GVWR on the frames.

The major issue with doing a cab swap, to my understanding, is that there is a difference in the location of the core support - the square body frame is longer in front of the cab than the 67-72 frame. I did not compare the cab mount locations, but the square body's rear mount is definitely taller and would have to be modified.

The reference I made to the K20 somewhere earlier in the thread was with regards to hangars. The K20 and K30 trucks share their front springs, mounts and hangars. The sway bars are not the same, but the mounting points are.

So, my original plan was to buy axles and springs from a square body, then find a 67-72 K20 donor frame for all of the front hangars, etc. However, I happened to get a REALLY good deal on a complete truck with a rusty frame, so that made the most sense for my project.

I cannot verify this myself, but I believe the frames in the early square body K30 (1978 - 1980) is different than the 1981+ frame, which is ASYMMETRIC in the front, which created some issues for me with the cross members. Nothing undoable, just food for thought.

Thanks. Still kicking around the idea. Sounds like it would be easier to find a K20 chassis and then stick the one ton axles underneath. The only thing I am not sure on these year trucks (67-72) are how much heavier the 30 series is over the 20 series. I have come across an 85 k30 chassis that I could get the axles off of but would have to find a hydroboost set up. It's coming down whether I want to sell my 86 K30 to fund the project.