Anybody consider running a Cummins 4BTA under the hood of a 3100 series? I've found some on the internet with TH400 trannies - apparently with Chevy compatible motor mounts. Everything I've ever heard about them has been impressive. My wife's big Gen I 1 ton Dodge is pulling 18 mpg (city driving!) out of the related 6BT - and the truck weighs double what most vehicles do. I've heard gearing the 4BTA appropriately should result in 30+mpg, while hopping it up to 250 hp and ungodly levels of torque is possible as well.
