His description sounds like it lost prime/somehow got an air pocket trapped inside. He might want to try replacing the oil filter and completely filling the new filter with oil (may take over an hour for it to soak into the element) to see if that makes any difference.

He also might want to try loosening the filter and/or loosening the oil pressure sender, starting it, allowing it to make a mess for a second and then trying again. The idea is to purge air.

If none of that gets it, then....

Don't blame him a bit for wanting to put a pump in it, but they aren't ridiculously prone to failure.

If he's set on doing the pump, I'd probably shotgun it/do the pump along with the stuff below to make sure it isn't sucking or pushing air.

There is an O ring between the oil filter adapter and the block that might be slowly failing/might be twisted in the groove or something (Actually I'd probably do that first since it's the least invasive, and should take under and hour to replace).

Also the pickup tube has a o ring that can potentially fail. The pickup tube mounting flange is, if I remember right, swedged on (not welded), and I would want to make sure the whole pickup tube is air tight. I would also check out the pickup to pan clearance.

Broken spring means the lifter could have been launched upward enough to expose the oil passage to air. Hopefully the lifter retaining yoke is still in good shape...unfortunately the only way to inspect it is to remove that head. It's probably fine, they are not known to break even though they're made of plastic.

About the only good news in the whole deal is...once everything around the radiator + the upper core support is removed, it makes a fairly comfortable place to sit/stand and work on it. Having done a couple top end + cam + header jobs I can say from experience....the trucks are MUCH easier to work on than the same engine in a car chassis.

The pump wraps around the crankshaft in the front, btw.