I have a 57 NAPCO panel with the original 4 speed tranny. There is an intermediate shaft between the tranny and the transfer case. So I'm looking for a 5 or 6 speed, 2WD tranny that will handle 6000 lbs. 3.91 gears, I'd be happy to have a bellhousing made. All the trannys I find don't look heavy enough to handle the load. Any suggestions?