need a replacement tranny compatible w my 84 diesel Isuzu
 

Hey there, y'all. Just got the stock 84 Chevy S10 with an Isuzu 2.2L diesel engine. rear wheel drive. 5 speed. Got scammed! its a great truck but the tranny was shot. If I'd test driven it for 20 minutes more I'd have saved myself a lot of headache. The guy is unreachable, unfindable. anyway....
I'm learning that there is a bit of wiggle room with what kinds of trannies will match up to my Isuzu engine. It had a T5 Borg Warner tranny. apparently they made 2 that year. this car had the early model. If I remember correctly, the bell housing could be detached from the tranny I had. I've got a tranny mechanic (good guy) looking to see if he can make shift something, but I need to find the plan B new used one in case he can't make it work.
I've been told that what matters is that the bolt pattern matches, and is compatible with the size engine I have. If I wanted, I could switch to a four speed, or even get an automatic tranny. I don't even think it has to be from a diesel engine.
I want to start calling around to junk yards and asking if they have what I need, but I'm still not sure exactly what specs to tell them so they know exactly what they're looking for.
You're help is appreciated!!!