1971 340 water pump and crank pulley problem

he double pulley alternator only works with A/C....AFAIK. You can pull it off there with the right tool, and push on a single until it lines up, usually "all the way". The crank pulley should work regardless, but I think you have an early wp pulley on the pump, which will have to be swapped out.
I'm sorta guessing
If you intend on hitting the 6000s you gotta get the pulley alignment bang-on.

I think you're gonna need more fan tho, and probably a shroud, and probably a restrictor in that looped heater hose.and that top hose is gonna make trouble at high-rpm. These are not picking on your combo, I'm jus saying keep a close eye on your temp gauge.