a few questions on my '77 resto/custom job

[chevysnbuicks]

Ok, hopefully some of you glanced at my new member thread post, so you'll have an idea of what I'm doing.

Ok, my stock gas tank on the passenger side hangs too low for what I'm doing (air bags, hopefully laying frame) so [someone] at FSC suggested a fuel cell, which I had considered. The problem, I need it to fit UNDER the bed, it needs to be at LEAST 15 gallons, it can't sit below the bottom of the frame rails, and I still have to have room for air tanks and compressors somewhere. What would y'all suggest me doing?

I've been told that it won't lay frame without either raising the cross member or z-ing the frame. Honestly, z-ing the frame sounds a little too difficult/complex for me, and I've heard it looks kind of tacky after it's done. does anyone have any good (lots of pictures, and a good step by step to go along with it) tutorials for raising the cross member?

Also, do I really need to get new A-arms built for bags, or will 2" or 2 1/2" drop spindles with stock arms allow it to drop enough?

and one last question that I can think of right now. I am not sure of what size rim I want to use. I know I'll have to tub the firewall to tuck 20s in the front, and I'll have to tub the rear anyway. What about 18s? are they that hard to fit with a decent amount of rubber? I've conisdered 17s with lots of rubber, but I don't know if it'll look that good with the style I'm doing (gothic/sinister style... gotta love it).

Anyway, thanks in advance, I'm sure I'll have more questions later. Actually I promise I'll have some later. I want to be as prepared for this as possible before I even start.