The deuce multifuel will work with the proper additions. If you try to use a deuce transmission, you will need an adapter machined to fit the deuce output on the transmission to the large flange the five ton has on the transmission-transfer case shaft.
If you get a bell housing,and clutch assembly off a 5 ton multifuel, you can fit the deuce motor directly to the 5 ton transmission, I think the gas motor one, but I have not tried that. Maybe someone else on here has and can comment.
You will also need the 5 ton front motor mount fork instead of the one for the deuce.
You will need the power steering pump off a 5 ton motor.
The five ton motor leans to one side a bit, so the fan shroud on the radiator is offset. The one for the 602 is centered I believe, so some modification needed here.
You will need a fuel return line to your fuel tank and a fuel boost pump in the tank or mounted external at the tank.
The exhaust system will be entirely different, but you can probably modify yours to work if you do not mind an under chassis exhaust system.
Your accelerator linkage will need modification.
You will need to install a fuel on/off cable.
The air compressors are on different sides and at different levels, so some piping modifications needed here.
The five ton oil pan is reversed from the deuce, but it is the same pan, just reversed. You will then need the 5 ton oil pump piping because it is entirely different since the deep end of the pan has switched ends now.
There are probably some other details that have slipped my memory, but these are the ones that come to mind right now.
As you can see, a lot changes, but if you want to take on the project, it can be done. A multifuel motor out of a donor 5 ton would make it much simpler!
Regards Marti