I drove some GMC trucks with the 478. Way to heavy for anything under a 2 ton. Most were in a 5 or 10 ton. If you put in something, don't run it WOT for any length of time. One truck we had was geared to a max speed of 62 mph, and used for highway travel. At about 100,000 miles I put a rod through the block on the 3rd engine. Truck was sold to a farmer. For info, go to Jolly's site
www.6066gmcguy.com/EngineData.html. For mileage, it wasn't bad. Don't think I ever emptied both tanks (100 gal.) in a day, many days were 500-600 miles. Not bad for hauling 15 tons of lumber.
