I think many GMs used same whole pump assembly, metal tanks not meant to be pryed on were and was the biggest problem. Whole used was fast and easy THEN but now this old could be trouble for a good whole unit.
Pump itself is still available w tank for about $50 so just need to swap the pulley. I wouldn't bother messing with repairing existing one on this especially unless no other choices easy.
No cap so need your old one on this. Good time to do the hoses too.
Bleeding out was just filling reservoir and steering fully left and right. Front wheels hoisted was better, no load till finished.
What model? That was a look up for a Lemans but may fit many as said.
If run dry too long you may have damaged the steering gearbox?