Picking up first big rig lots of questions, 1969 Chev

[67chevy_hotrod]

Hey y'all, just about to get my hands on a 1969 Chev c40/50/60. First question is how does one tell whether it's a 40 a 50 or 60? The GVWR on the tag of the door says 22,000 pounds. It's got 10 lug Widowmaker Wheels and I was wondering what a safe alternative is or if I need to swap axles? It's a small block with a ch465 and two speed rear end. I plan on just turning it into a big service truck that I can haul a dump trailer behind and probably throwing a big block in it. If anyone's got any helpful hints or wisdom regarding ways to cost-effectively update things on a truck this big I am all ears! Thanks much and I will post pictures soon!