Trans looks like an IH T18 to me. If the bolt holes in the transmission for the bellhousing are threaded it's definitely IH. The bellhousing/transmission bolts thread into the trans from inside the bell with IH T18s.
Not sure why the frame sticks past the rear unless I'm missing something. ??
Get some frame pictures. Now that you mention it, I see a frame crossmember from the engine compartment laying the back of your Scrambler. The old Willys frames had a round tube in the front. It looks to be some sort of FrankenJeep. Even at that, the body is still pretty serviceable.
"Work hard, rock hard, eat hard, sleep hard, grow big, wear glasses if you need 'em."