I had an IDI for quite a few years, should have never sold it. 4.11:1 rear gear with a ZF5 transmission. Never took off in first, first was a granny low gear. Tore the engine down for a complete reseal at 500,000 miles and there was still faint cross hatch in the cylinder walls. I beat that truck like a red headed step child from the time I was 15 to the time I was 22 and sold it cheap. Guy i sold it to yanked the trans and engine and dropped it into a tube chassis toy on 44's and finally popped the engine this past spring after nearly 5 more years. When he bought it, the odo was rolled over 7 times and was at 725,000 miles. That truck had no problem getting started in 1st or 2nd pulling a loaded 25ft goose neck. Getting up to highway speed with the 38's I ran on it was a different story. Biggest thing to watch is if the water pump goes out watch the casting on the new one. They had a thin casting and a thick casting. If you put the long bolts from the thick pump on the thin pump you would run the bolts thru the cover into the timing chain between the cam and IP.
If you wanna build a little more power, you can usually find someone selling a banks sidewinder turbo set for one prety cheap. Also a set of injectors can be had dirt cheap, look into marine injectors. Found with the injectors out of an old IH versatile (IIRC they were g-code) with about 8* of timing advance and turn the pump up about 4-5 flats would build alot of power naturally aspirated. They were a bullet proof power plant with a lot of potential that was never truly unleashed since right as the diesel game started taking off, they went to electronically controlled so a chip was easier on the old psds
