I've got a '41 1 1/2 ton as well and have been toying with the idea of doing a similar swap to retire the 216 splasher and crash box. The 292 with a syncro box would be a killer combo, but would be way more involved than upgrading to an earlier full pressure engine. Here is a short list of some(but I'm sure not all)of the obstacles I see and possible solutions.
1)292 has side instead of front mounts. Will have to fabricate or buy an after market side mount set up.
2)Will have to use the later syle bell housing with different rear mounts. Will either have to modify the crossmember or possibly adapt one from a later truck. The one in your '70 may work.
3)The trucks designed pre-WW2 have the clutch and brake pedals mounted on the bellhousing you will replace. My idea (which I haven't tried or seen done yet) would be to adapt a pedal mount from an AD or Task Force series truck. It would probably involve at the least, drilling mounting holes in the frame and modifying the pedal arms to locate the pedals and match the angle of the toe board. There may be a easier way and I'd be intersted in hearing other members ideas on this.
4)The battery box may need to be relocated to clear the syncro box. That may not be a bad thing. I'm not too fond of unbolting the floorboards to remove the battery from the stock location.
5)Depending on what trans. you use, you may have to make a bracket for the parking brake and maybe modify the floorboard to work with it and the shift tower on the new trans..
6)The drive line may need shortened. When shortening it you could have the yoke changed to match the one on the trans. if it's different. If it doesen't need cut they make crossover u-joints to hook it up if they are different.
Along with the previous post, I think those would be the big issues. With all involved, Im also considering going with a 261 or 235 with AD bellhousing
modified by Jim Carter to mount the pedals with a SM420 or a NP435 that I have. I haven't done either swap before but have been studying it for a while. Hopefully some of the other members can add (or subtract if I'm on the wrong track)to this.
