Need some suspension/chassis guidance

Knowing what you have right now for a rear axle would be helpful for determining which would be the most beneficial way for you to go. For example, if you have a 7 1/4, nobody is going to tell you to waste money narrowing that. Assuming you have an 8 3/4, which one, A-body SBP or BBP, B-body? How much are you willing to spend? What tools do you have access to? Can you weld? Are you planning to do all the work yourself? Have you ever done a 4-link before? Those are just a few questions I came up with off the top of my head.