I can't believe i'm about to mention this but this thread seems to be the "Land of the big ideas" so.......
Here is what I would do........
Find an old semi cab because they are really big. Then cut the roof off and make it look like big a** T Bucket. Look at some of the older semi cab they look just like a big version of a 32 Ford, even the grill is the same but 4 times the size.
Anyhow, Forget the typical tires and just go with duels on the back so you can make it simple.
For the frame use big I beams from a structural building component company. Find a set of thin tires for the front, and use just the grill with an open diesel engine. Just think of the gas mileage.
For the back you have a couple options. One is to use one of the side fuel tanks and mount it on the back. Another idea is to use a diamond plate tool box for the pick-up bed.
Throw some smoke stacks on her and you have yourself one heck of a conversation piece that just fits in a garage.
For the front axel talk to Ron at RPM and have him bend and shape you one out of a rail road track.
The best part is you can fit four or five people in it and still have the look of a normal T Bucket!
Mike