Sorry to hear about your bad luck,,been there done that,,it is frustrating,,
rest easy thougha good fe with a rev linit,,used like it is built to be used is bullet proof,,and the most satisfying motor in exsistance I think,something was just wrong,,I had a simular thing happen once with a 427,this sounds stupid,but I put a rod bearing in backwards,I assembled with plasti guage,when i took it apart to check,,I guess I put the little tab on the wrong side of the cap,tightening the cap crunched it against the rod cap,,making it seize,I caught hell for it too,it was a new service block and crank with all holman moody stuff,,I believe your problem is connected to your
oil pressure,my motor cold rolls the guage past 100 and up to 5,,never gets below 50,,
I hope your builder can figure it out,,have in there,,Tk