Actually, the distributor turns at the exact speed as the cam, which is half the speed of the crankshaft.
Finding TDC with the rotor pointing at #1 is inaccurate at best..... doesn't account for base advance, chain slop, and eyeballin' it.
Sounds like you have a running engine..... if there's room, I'd swap that vac advance with dist. IN the truck, that way timing is still close!
