18" rim pics on Demon or Dusters

With the right back spacing you should be able to fit a 255/40 in the rear wheel well, maybe need offset hangers for the leafs. I have my Demon minitubed and now have room for 345 wide rubber tucked up in wheel well, but I also have link mounts on frame rail now. 18s are a nice size, look good on A-Bodies and don't look ghetto with rubber band rubber.
Grab a ruler and a string with plumbob and you'll get it figured out if you already haven't...cheers.