I would bet that the engine was rebuilt - but all the accessories are the same ones that were on there before - PS pump, Alt., Smog Pump, etc.
If the smog pump took a dump, it can clog the air pipes into the exhaust, which may raise back pressure and if the belt is seized could account for the idling problems, smoke, and stink.
Low oil may not be related. These truck are like tanks, and pretty much run inspite of any abuse. I would focus on the accessories and Smog system first, then work my way into the engine if that is not the problem.
M
If the smog pump took a dump, it can clog the air pipes into the exhaust, which may raise back pressure and if the belt is seized could account for the idling problems, smoke, and stink.
Low oil may not be related. These truck are like tanks, and pretty much run inspite of any abuse. I would focus on the accessories and Smog system first, then work my way into the engine if that is not the problem.
M