Want to drop rear about 1 inch more and better ride

[a32axo]

What's up, got a 1970 gmc c15 shortbed.
Front drop with 2.5 spindles and og coils cut 1 turn
Rear major ? It has 3 leafs only. A lot of bed roll shocks prolly gone
From floor to gender lip 28 inches front 31 inches rear
Got more wheel gap in rear fronts are tucked
What's the best way to get the rear to where I want it about
1-2 inches lower.