You've got two actions running here. First is using the B-body axle. The second is using 18 inch wheels.
The B-body axle is at least 1.375 inches longer drum to drum.
http://www.moparts.org/Tech/Archive/axle/17.html
The B-body spring perches are one inch farther apart than the A-body. They will need to be carefully removed and re-welded in the proper location.
Regarding the wheels, I spoke with Stockton Wheel, a long time ago, who told me the largest wheel/tire package that will fit within the A-body wheel well is a 235/60-15. That equates to 26.1" diameter and 9.5" width. If you can come up with an 18" wheel/tire package that will fit that criteria, you should be good to go.[/QUOTE
I have 28in on there already.... on 15x8..Already..
