5.9 slt plus Durango donor for 74 duster
mine's been over 5.5K a few times.
kinda easy with the 3.92 rear and some ahem, traction issues inherent with a truck
...and with those gears it moves my 4200# Dakota pretty well, even with 55 series tires on 17" wheels.
Also still alive and strong as the day I bought it at 167,000 miles.