I'm going to run some 63" rear leafs on my 86 k5, Do you know what a goo year to get them out of, also are they 5 or 4 leaf pack. I think the 5 leaf pack has like an over load spring on it, that would take out some of the flex right.
I'm not sure on the 63" leafs. I know that there are diffs on the Ford rear spring swap. I would leave the overload on there. Maybe cut it down or flip it over. I took them off and the extra flex trashed out my rear springs.