jack the frame enough to take weight of truck but leave weight of axle and springs sitting on the ground, some trial and error, then spring pin/bolt will be approximately free.

It'd be wise to use jack stands under frame to support it while doing your work.

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
---All pictures---
"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-