With that kind of budget you shouldn't have a problem finding a good IDI diesel truck around here.
88-92 pretty much has you stuck with either a ZF 5 speed for a manual or a E4OD for an automatic. Both are solid units if properly maintained. I'd vouch for the cast iron tank that the T19 4 speed manual transmission is if you want something you can't kill.
Generally these IDI engines are designed to be easy to work on, generally inexpensive to repair relative to their direct injection cousins, and very reliable.
These are no egos here, so feel free to ask anything, you will get a real and honest reply.
Check out the various reference threads, they cover a lot of common questions, symptoms and fixes.
Once you get a truck, put its info in your signature so that we don't have to keep asking what you have.