well, we know that diesel contains more energy per gallon than gasoline, so i don't see this being more efficient.
as for putting a carb on top of a diesel, well how do you feel about blowing up your engine - the heat of compression would ignite the fuel mix way too early and have nasty detonation effects on the engine.
doesn't look like one i would want to try unless my goal was experimenting on something that was about to be sent to the crusher anyway
my van, 87 e350, 6.9 NA, c6, 3.55s with a powertrax locker and 225/70r19.5 michelin tires. built out with toolboxes and onboard 120v power and compressed air powered by twin 3g alternators