Another option to supplement your pack is some from an s10. They are spring under from the factory and have pretty good arch.
That's what I ran/run until I pulled that rig apart
. They worked fantastic and flexed like crazy, They only gave me about 3-4 inches of total lift from stock so I had some 2' alloy blocks. I was looking for some 63's but now that I've read this thread I think I will put them back on this rig as well and just go with a little longer shackle, this rig will not sit as high as the other did. s10 springs are 25.5 eyehole to center both directions with no weight on them. Weighted I think they are about 56" long
With the s10 springs you will have to move the front perches up on the frame about 5" but thats super easy for anybody with a welder. (and there's plenty of them on here that would be willing to help I'm sure)
Good luck
Thanks for the awesome thread guys, made up my mind for me