I had an '82 K5 Blazer with one in it. It had the 4L60E transmission (Turbo350 with a 4th gear) and a 3.08 rear end gear. Good motor. Killed transmissions. Too much low RPM torque, I guess. The truck weighed 6000 lbs with just me in it. It got about 15.5 MPG all around and between 19 and 21 MPFG on hte highway at moderate speeds. Towing my 20' Shasta travel trailer, I got 11 MPG- up hills, down hills, fast or slow.
Besides the transmission issues, I only had a couple of problems. Glow plug controller had issues and killed glow plug regularly. Finally broke down and spent the bucks (about $150) and bought new controller. Problems solved. Other issue was that the injection pump developed a leak, while I was driving. Fuel was in the valley between the heads (where the pump is mounted) and running down the driver's side of the engine onto the exhaust manifold. Smoked like crazy, but never caught fire. Had the pump rebuilt and solved that problem for good. Motor ran fine and the 4WD was real handy. Had automatic hubs and I had to replace one of them one time.
Overall truck ran pretty well for non-turbo motor. About 130HP, which was fine with me. I finally sold it when the transmission went out for the 5th time!