It's probably a CJ7 frame. It could also be a shortened Wagoneer or J10 frame.
A TH400 Quadratrac is the Jeep drivetrain used in FSJ's and a few CJ7's '79 and '78. It is an AMC bellhousing, GM TH400 guts, and a strange Chysler 2WD outpat shaft that sticks way out specifically to mate to a Borg Warner full time transfer case. The rear bolt pattern was the same as any other TH400, but it was clocked differently. The whole casting appears warped to one side.
Some other Jeeps used GM TH400s with BOP to AMC adaptor pieces and a rear texas pattern adaptor, different output shaft, and Dana20. The AMC TH400 is a completely different casting only ever used with that specific transfer case.