Diesel Swap
 

At the risk of unleashing a firestorm of criticism, I would like to ask if anyone has swapped a 12valve Cummins into their 60-66 gmc? I have a 1 Ton dually and the original engine is long gone. It has a small block 350 now. It runs good but it does not have the power to pull the trailer with my antique tractor on it. I would also like to upgrade from the farmer 4 speed to a 5 or 6 gear transmission. Any constructive comments will be appreciated.