Hello Folks, I'm the new guy with a new to me M715. I have wanted one of these trucks since I first drove one in 1977 while on Enewetak Atoll. I'm going through the options of what to do and what needs to be done. The first ticket item is the engine, it needs a small block. The second item is the gear ratio of the diffs. I've had it up to 55 so far but I swear it's going to explode if I stayed there long. I have looked everywhere for a set of R:4.56:1 ring & pinion sets but nobody has them. I keep hearing it's best to install diffs from a more current truck. Looking for your experienced input. Thanks.