suspension options 3/4 ton

[BurnerBrown]

I have a 68 GMC 2500. I want to keep the heavier suspension so I can load it up. But I also would like to lower the truck front and rear, and not lose too much load capacity.
I am looking for opinions on the best way to go about this and how much can the truck be lowered using the 8 lug setup, without nothing the rear rails, or crossmember,etc. I could swap in a c-10 crossmember but then its a sagger when loaded. Does anyone make dropped spindles for a 3/4 ton? Should I swap in 73-87 crossmember, and suspension from a 3/4 ton, etc? The current leaf spring setup doesnt look to have much room to be lowered, if I flip the rear, I don't think it'll even clear the rails. I see 3/4 trucks lowered, not sure how its typically done.
As you can see, I'm not sure what direction to go.