Well that's very generous of the OP.
Main thing with the 6.5s is they're like the weaker cousin to the 6.0 Pstroke. They like their maintenance and require a lot of tinkering. The long block is not an inherently bad design and many higher mile trucks on original engines. The devil with them is GMs poor design of the peripheral systems to control that engine. Compare to the Cummins and Ford IH diesels of the day, they are a nightmare of switches, solenoids and odd ball control systems. Learn it, sort out the bad stuff and they're a nice little motor that gets decent mileage.