If you are burning a quart of oil every fifty miles and not leaking much then I would suspect that someone did not take proper care of the engine at some point in it's life. A compression test will tell you a lot more about the internals of your motor. What kind of mileage are you getting? Also is it a shortbed or a longbed? 4x4, 5 speed, 4 speed? A 4x4 with that kind of mileage would not surprise me being tired and ready for rebuild.
1984 diesel LS long bed 4x4
1983 diesel 4x2 long bed
1984 diesel 4x2 short bed MPG Plus
1984 diesel 4x2 automatic longbed
1982 diesel 4x4 LUV mikado shortbed
1986 gas LS 4x4 Trooper II 2 door
1984 turbodiesel 4x2 automatic longbed