you can get the 19gallon rci fuel cell and then remove the sender and drill a hole for your fuel pump to drop into and then just space it up 1/4" and make another plate to clamp it down. Ill have mine done this week sometime hopefully and ill post pics.
yea mine is going between my frame rails and it fits perfectly. mine is 12x12x30 and i believe its 32" between the rails. Its very simple to get it to work.