well, the weak springs could be affecting the pinion angle.
Also, they make 2,4,and 6 degree shims, wedges that go bewteen the axle and the leaf spring to change the angle of the pinion....do you have any of those installled? U should look into that first, and remove or reverse, or install if there isnt any there. thats how you adjust pinion angle (without cutting off and moving the spring perches).
Olivers drive shaft in Winston Salem does great work, and i think you will find many on this board will agree.