Many truck owners have their own personal preference, and will critique diesels other than their own. Any diesel engine is strong and reliable, and will run much longer than a gas engine, but routine maintenance is essential. The Cummins 5.9 Liter Engine is an extremely strong and reliable engine, with many still on the road after 200,000 miles or more. The Power Stroke 7.3 Liter, which is an option for Ford trucks, also lasts 200,000+ miles. The Duramax diesel, found in GMC's and Chevy's, is equally as strong. With routine maintenance, any diesel will run forever.
The Allison 1000 which is mated with the Duramax diesel
Dodge. Straight up.
The best dually diesel pickup truck would be Chevy or GMC 3500 with Duramax and Allison transmission.
The best mileage for a three quater ton diesel pickup truck is 15 mph. It will only change if you going on a stopping trip and you don't use a highway on a long trip.
Considering that a diesel pickup truck can't use gas I would say that there aren't any diesel trucks that get good gas mileage. If you were wondering which diesel truck gets the highest miles per gallon then I would say you should look at the Dodge Cummins diesel.
The best things about a diesel pickup truck are that you will not have to fill up the tank as ofter if you are driving a lot. Another advantage is that they have glow plugs and if you ever have a problem with starting you know where to check first.
Diesel engines were not a factory option until the late 70s, so if you find a 60s pickup with a diesel, it has been switched after it left the factory. Installing a diesel engine in a 60s model Ford pickup would not be the easiest conversion, but it could be done. Motor mounts would probably have to be fabricated, and you would probably have to change out the transmission, also. Best to find an engine/transmission combination that has already been proven to work together. The other consideration is finding a diesel engine with the horsepower and torque necessary for the truck.
Here's a few million mile pickup truck diesel engines - - - 7.3L IDI International (Ford), 6.9L IDI International (Ford), 7.3L Powerstroke Turbo Diesel (Ford), and the 5.9L Cummins I-6 engine (Dodge.) Of the newest diesel engines offered in the Big 3 trucks, I'd say #1 is the 6.7L Powerstroke Diesel, #2 6.6L Duramax, #3 6.7L Cummins.
The best gas mileage truck is the 2011 Ford F150's which get 23 MPG on the highway with the V6 engine.
The top makes for Diesel trucks are Ford, Dodge, and Chevrolet. The best selling Diesel seems to be the Ford F Series. The Duramax engine seems to get very good reviews. The Dodge seems to have more problems with it's engine.
According to many the Ford F-150 is the best selling pickup truck in the US. Ford.com has more info on this vehicle.
definitley diesel its a much more effecient engine and surprisingly burns much cleaner than gasoline especially in performance if you put 5grand into a diesel truck your lookin at close to 30 mpgs or more as to were a gasoline engine would be getting only about 8