A 453 Detroit is all you will want to go. Back before there were factory diesel PUs there was a couple guys out of Bakerfield getting 453s out of rail road reefer cars and rebuilding them. Only they went with 1 ton Internationals single rear wheel because they could cary the wait of the Detroit better. With an automatic they got 18 mpg, standard they were seeing 21 mpg. If they could get traction they would climb a telephone plole.
"The Constitution is not an instrument for the government to restrain the people, it is an instrument for the people to restrain the government."
-Patrick Henry
A5150nut
2006 K3500 D/A
94 6.5 4x4 5spd Sold