The Dodge is a little on the vintage side of the spectrum. However, I would strongly consider putting a Cummins BT 5.9L Diesel engine in the ‘75 through a 6spd manual gearbox and transfer case with a doubler on it. Not to mention an air locker in the front and back axles... it would be similar to a Walter setup almost.
As for the D4 that sounds like a great little dozer. Do you have more pictures? What are it’s specs dish about the technical features...
I laughed at this and the other responses - A fine idea to make it a Diesel - lol
yes some might say 1975 is "vintage"
the kids ride in it and call it "Old"
I was in high school then and still my thoughts are its not really old unless it is pre 1966 -
its all in your POV. lol
it has a tired 318 in it and I have been toying with the idea of replacing that with a 360 as it should be a swap that has minimal requirements and will bolt right into the running gear thats already in place.
the truck has maybe 92,000 miles on it
I put about 15 or so thousand on it since I bought it (sometime) in the 90's
its an ok 4x4 truck with the AT a custom two tone with all the chrome
it was pretty cherry when I first got it
it has the military running gear which is heavy duty with a top speed of 60
well it whines at 60 - it likes to roll along at 45 to 50
its a low geared hauler.
it makes an ok personal plow truck.
Now "IF" I were to put a diesel in anything -
there is this 1966 Nissan Patrol that would be a super rig to outfit it in a fashion as you describe - that would be a super cool project.
the D4 is around 1968 [so the CAT parts guy sez] it is a J series D4 and a bit smaller than my previous RD4 from the early thirties.