The nice thing about those old Allis Chalmers is they used a pair of six inch channel iron for the main frame. That means you can pull the engine without breaking the tractor in two parts. So, I got an old WD for scrap iron price with a froze and cracked block.

I am shopping around for a small diesel, but it is a lot easier to find a small four cylinder gas like a toyota or datson with more horsepower than the original Allis (only about 35 hp)

Here is a short video about this Farmall with a 4 cyl cummins:
[link to www.youtube.com (secure)]