i have these ford springs too, goin to put them on my 92 toy.  the stock toy springs are longer so it doesnt look like i will have to move the front hanger forward much more.  i mocked them up yesterday, it does however look as though i will need to move the shackle hanger forward a bit. had bad shackle angle testing it.

theoretically your shackle should be vertical or slightly forward when the springs have no load correct?

i have some new perchs to weld up on the axle to compensate for any rotation and to recenter the axle up.