I had exactly the same thing on breakin, luckily, my Son was watching the oil pressure gauge and we shut it down the second it hit zero. It turned out to be an oil galley plug in the timing chain area that blew out. The machine shop blamed it on "oil pressure spike" but I think they didn't strake it correctly. I tapped threads and put screw in plugs in their place, no more problems.

Not saying that is what you have (could be a broken oil pump drive shaft or something else), but it is one place to start looking. I rounded off the hex on a drive shaft one time and lost oil pressure immediately too.

Don