If I recall correctly, the vacuum line for the pressure regulator goes to a nipple on the big rubber hose that goes from the valve cover to the air cleaner.

You never said what model the car is, doesn't it have two fuel pumps?
Also you mentioned that you installed the pump and ovp, but what about the sender?
If there was a lot of sediment, and you beat on the tank, some of that loose debris could be the cause somehow. If the sender was crunched bad enough maybe it is possible that the tube cracked or broke and when the fuel level gets low enough it sucks air along with an insufficient amount of fuel, or sucked in some sediment that bypassed the screen and partially clogged the line or unit. Maybe the fuel pump check valve or accumulator is faulty or even the pressure regulator.
Definitely check the fuel pressure/flow to rule some of these out.

I would first suspect anything you tinkered with between the last good ride and the when it went bad. Besides the tank, did you mess with anything under the hood while it was down?