Losing oil pressure at highway speed on a new engine is not a good thing! it sounds like the engine was not cleaned well on the second buildup, and debris circulating with the oil has trashed the rod and main bearings again. I never attempt a partial buildup after any oil-related failure- - - -the engine comes down to a bare block again and all the oil passages get brushed out and pressure washed. Your first clue should have been the lifter noise. The beginning of a debris-related failure usually clogs the one-way valves in the lifters, allowing them to collapse under load.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!