Leveling stock 1971 C10?

[Roadmarks]

I have a 1971 C10 that I have dragged kicking and screaming back from the edge of the abyss. I won't know what all I have done until I go through the huge box of receipts. Anyway, it's an LWB with 255/60X15s on 8" 'Vette style Rallyes. Problem is it sits unlevel front to back and rear high. It looks to me like the rear needs to come down 2-3" to be level. Can someone explain the best way to approach this? I hesitate to heat the springs. What are my options? It is a coil spring/trailing arm truck.

thanks in advance,

Les