On a flat tappet cam run it 20- 30 mins varying rpms from 2500-3000 for first 5 mins. Then vary rpms at 1500-2500 for 15 mins. Then let it run at 1200-1800 for 10 mins. After that take it easy with only short WOT bursts for first hour and check oil and engine over for leaks frequently. The only reason I say to take it easy for the first hour is because usually with a rebuild comes a few upgrades and you don't want to lean out the engine.