As far as most practical, the cummins 4BT, that's like in the dodge truck but only 4 cylinders.

The 6 cylinder from the dodge is going to be too long to make it an easy conversion, and you will want a 1 ton truck or better to start with, or at least I would.

I am doing the Detroit 4-53T conversion, check out the pictures on the link below.

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-