91-2001 6.5 turbo diesel in any LT (1/2-1 ton) chevy/GMC chassis. Early ones (91-93) are mechanical injection pumps, 94-2001 are electronically controlled by an ECM.
Around 200 HP, but 430 FT/LBS of torque at 1800 RPM. I have a 93 K3500 4X4 dually, and an 95 C3500HD (15,000 GVW) box truck, both 4L80E transmissions. A good tow vehicle in my estimation, and because they're a turbo diesel, good fuel economy.
Parts are reasonable, and you don't have to be a diesel technician to keep them running. You'll have no problem towing a 7,000 lb car and trailer with one of these. Open the exhaust to 4 inch tube, and richen the pump up a bit is all you need to get some more power out of one of these trucks. Simple and cheap to modify for a little extra power. They made a lot of them, so they're not hard to find used.
The early IDI diesel, IH 7.3 engines, as well as the later Powerstroke turbo in light duty fords. Simple engines that put out decent power for dollars spent. I have an 88 IH 2 ton chassis wrecker (Ex U Haul straight truck that I shortened the chassis) with the 7.3 IDI diesel that pulls very well for a naturally aspirated diesel. I only paid $1800 for the cab and chassis from U Haul, with a fresh short block that has under 10,000 miles on it.
