I dropped my 69 with 2 1/2" spindles and 2" springs in the front. I did an axle flip in the back and my truck has the HD rear leaf package. Not sure if that drops it less because they have more arch or more because more leafs, but the net effect was a 7" drop. I can haul 500# in the bed without hitting the frame...much. I cut the bumpstop pads off the axle housing and installed the urethane pads that came with the DJM flip kit. That made all the difference. I used front shocks all around and drilled the opposite side of the bracket in the rear and used new front shock studs to move the shock more vertical.
I see just 3 ways or combos to get there:
1) shackles get you 1 1/2" drop.
2) drop leaf springs with your choice of drop
3) axle flip = 7".
So if you want something between 1 1/2" and 7" you need to buy springs. I would do the 4" and keep the shackles in my back pocket as an option to go to 5-6" drop.
Big tires are what makes the drop work IMO. I went 27" tall front and 29" tall rear. 235 55 17 on 17x8 with 4.5" bs and 275 55 17 on 17x9 with 5" bs. That's the biggest tire that will fit on a step without modifying inner bed sides.
