the 4jb1t will fit easily in your trooper, but be sure to get a tranny with it as it is not compatible with your msg that is behind your diesel now. i did the swap in my 86 and it did not require much, in m,y opinion. also, the 3.1 can fit with similar ease i am told. no direct experience with it personally, however. sounds like you are having rough times, my condolences on your hardships.

86 Turbo Diesel 4dr Trooper 4JB1TC
89 turbo diesel Trooper-RED