I'd think the shop doing the work should have this information. Or at least based on truck height, weight load, spring width, thickness of the leaves, number of leaves, etc should be able to go from there. I don't recall ever seeing this in any of the manuals. Actually I don't recall any of the manuals discussing re-arching springs. There is a place in Dallas that has been in business since Dallas was a small town. Truett-Worrall is the name, and I'd bet they would know what is needed. Good luck.


~ Jon
1952 1/2 ton with 1959 235 | T5 with 3.07 rear end