Ok...
Lots of possibilities. Some that come to mind....broken
oil pump shaft,
oil pump bolts loosened up,
oil pickup fell too close to pan, etc.
Here's what I would do first to rule some things out.
Take an electric drill and a pump primer, yank the distributor out, and prime the oil pump. Pull the valve covers, and see if you get oil to the top of the engine and watch the oil pressure gauge.