I have owned a 1999 and a 2004 Chevy 2500HD 4x4's. One I bought both new, and wish I had never sold the 1999! The 7.4 would pull anything and run forever. The 2004 had a 6.0 and was absolutely gutless in the mountains. Plus, the 1999 got better gas mileage! I would stick with the 7.4. Just regrind the crank, new pistons and rings (std) and replace the lifters. If yours is like mine was there was no wear on the valves, and the rebuild should take one weekend and cost about $800. Buy parts with GM part numbers on eBay. After all, it is a farm truck. Don't go crazy... make it reliable, and call it good.