I just went through my dad's 70 C50 this fall. It's a decent truck but rusty. Mechanically, I've got it fixed up nice. Had to rework several things the previous owner cobbled or just left broken. Now dad drives it like an oversized pick-up. He hauls a few bags of feed or 6 ton of rock on it. The only pricey item to worry about would be the hydrovac but they are still readily available.
Scott