Looking for a diesel to out in a 36 Mack... Looking for hp/tq bang for buck. Power stroke, 4bt,6bt,24valve etc?
I am not one to dictate what is BEST for a diesel... It all is personal preference in my opinion.
I have a 93 Cummins 6BT, I think it is perfect for a rat rod.
The Cummins industrial engine is fairly available in all kinds of things, and has a bunch of available power depending on the setup.
If I was to do it all over again, I would still go with a Cummins 6BT in the intercooled range of 1994 to 1996 I believe.
Some things I would hunt for:
Cummins 6BT from a Truck... Not an industrial one or from a F600/F700. With a truck donor you will have all kinds of stuff to use (Power steering Pump, Radiator Hoses, Radiator, Car stuff you will end up buying instead of having on hand)
Look for a P Pump... quite a bit easier to tune for power and the pump looks cooler.... I have the VE pump that will still be able to produce 450 HP safely.... The P-Pump will crank out much more easier.
If you have the room in the cab for a clutch pedal go with a manual trans... the setup of the automatic transmission with pressure (Hobbs) switches is proving to be slightly difficult and you will save space with a usually shorter and stalkier trans than compared to an automatic. You will appreciate the cab room you gain with the trans not eating it up.
The Cummins 6BT is truly a 2 wire hook up to run... One to the Fuel Shut Off, and one to engage the starter.... they have a cold start +12V heater grid on the heater but its not necessary. So you get a flip switch and a push button and get on to cranking the beast up.... Plus the wire to the alternator to get some +12 back to your battery or batteries.
You may be able to source a 6BT from a Bread Truck or delivery truck.
Don't rule out a rolled or salvage truck from an auction... It is unlikely to find these Cummins trucks at salvage yards... at least I haven't found one yet here in Michigan.
Try Searching Craigslist via Search Tempest (a search aggregator for Craigslist) for the following "Cummins, Cummings, 6BT, Intercooler, P Pump, Diesel, Deisel, 4BT, Onan, bread truck, Doritio, Lays, and Turbo" You will be digging through all kinds of stuff with those search terms but you will come across some guys that cant sell their stuff because their spelling isn't the greatest....
Hope that helps,