Gas tank alternatives for a 72

[nuke82]

Hey guys, I'm trying to fit a gas tank outside of the cab on my 72 swb truck and am having some troubles. The conventional alternative (blazer/surburban tank) doesn't work on my truck. The frame used to be a long bed frame and was cut down to fit a short bed, this was done by cutting the rear 12" or so off. Are there any other tanks that will work on these trucks that anyone has seen?

I've tried tracking down factory saddle tanks to no avail, would a saddle tank from a 73-87 model work?

The only other option I can think of....Since I am running a Ford 9" with leaf springs I no long have the rear coil spring bars (torsion bars?) in front of the differential, would a 90's model tank slip in there? I may have to convince the local salvage to loan me one and do a fit check...