RUN, do not walk away from anyone who reccomends STP for break-in. Back when I used STP for engine assembly, I had repeated oil-related failures for no good reason, mostly premature rod or main bearing wear. I even built one more engine that way, just to convince myself it was a fluke- - - - -nope, same results, a scored main bearing! Otherwise, you've gotten some good advice. The high-idle break-in is necessary to assure plenty of splash lubrication to the cam and lifters while they're establishing a running fit with each other. Make sure you've got plenty of cooling, maybe a fan or squirrel-cage blower aimed at the radiator during the initial run-in is helpful.
Jerry

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