While I personally have no problems with the Detroit 6.2 / 6.5s I personally would not bother swapping one into a tow rig. Those engines are light duty diesels that are designed to be good mileage getters, not workhorses. They'd have a much better reputation if they were installed into some of the lighter more aerodynamic mid 80's cars instead.
If I was to do a diesel swap, I'd probally go with a 5.9 Cummins myself. While a newer PowerStroke, or Duramax would be very cool, and would perform very well as they do in the new trucks, they are far more complicated, and far more expensive than the older 5.9 Cummins diesels are.
Installing a 5.9 does take a bit of work though. Couple of problems associated:
1. Firewall to engine clearance -- The 5.9 is a very big engine, and you will either need to "customize" your firewall with a big hammer, or put a 3" body lift on.
2. Oil pan to engine crossmember clearance -- The 5.9's oil pan contacts the front crossmember on your truck, and the pulleys sit very close too. You'll etiher need to make a custom engine crossmember, or buy an aftermarket oil pan of some sort.
3. The 5.9 needs a big radiator to keep cool -- This means you'll need to do some significant modifications to your rad support to pack both the rad, and the intercooler in.
4. The 5.9 is an extremely heavy engine -- They weigh close to 1000 lbs, while most small blocks weigh closer to 300 - 400 lbs tops. You will absolutely have to upgrade your front suspension to accomodate. Think D60 + add-a-leaves
5. If you are running AC, you'll need to move the AC compressor from the bottom of the engine to the top of the engine using an industrial tractor bracket that is available
6. You will need to switch to hydroboost brakes, as a diesel engine produces no vaccum, and a vaccum pump will not keep up with braking demands
7. Wiring -- you'll need to run the glow plug controller, and if you get a 94 or newer Cummins, you'll need to hook up the ECM stuff for the electronic injection
8. Transmission -- you'll need to either find an adapter to hook the Chevy engine / transmission up, or you'll need to run the Dodge transmission + t-case
9. Fuel system -- you'll need to find / buy a new Diesel fuel tank. Your gasoline tank has a galvanizing coating inside which will be broken down by the diesel and plated onto the inside of your 600 dollar IP, effectively ruining it
10. Exhaust -- You want very free flowing exhaust for any diesel, so expect to spend a fair bit of money on a big diameter mandrel bent exhaust system to provide as much.
11. Engine Mounts -- There are a number of companies / individuals out there that you can buy pre-made conversion mounts that either mount to your stock chevy engine mount faces, or even use the factory chevy style engine mount.
Buy a complete, running donor vehicle. Nothing sucks worse than getting nickled and dimed to death on small stuff that doesn't come with a "complete" engine / tranny setup that you buy seperate from a donor vehicle. This is a lesson I learned the hard way swapping a TPI setup into my truck...
If I ever find a cheap 5.9/NV4500 truck, I'd definitely consider this swap, but would be expecting to spend at least 4 - 5000 on the swap, not including the donor truck... Some guys get it done for as little as 2500, including the donor, but I wouldn't count on it for sure! Some guys have spent over 10k getting it done, but usually they get someone else to do it for them...
So, in short, do your research before you leap headfirst into anything. Its all very possible, and lots of people have done these swaps before you, so learn from their discoveries / mistakes, and you'll do it for the best price possible. Also, take any estimate of cost, and triple it, and think if you're still willing to go for it or not. Maybe you'll be correct in your estimate, but usually that isn't the case.
