Plugging the dipstick port:
My engine builder (Steve Carbone-Former Top Fuel Builder and Champion) that built several of my race engines did it because we always changed the
oil after a meet and there was no way for
oil to blow by a dipstick. In the beginning we would blow
oil out of the dipstick during some aggressive driving. After we plugged the dipstick with a metal plug that leak never occurred again. We found that the adaptor for the remote oil filter and dipstick combo was leaking oil and it was migrating to the back of the engine making it appear the rear main was bad. After using some dye in the oil and a dyno run we found where most of the leak was coming from (the other leak was the back of the intake and rear of the valve covers. This engine was built to handle 7000 RPM which it did for several years until one day at Texas Motor Speedway I asked for a little more RPM which it didn't like too much.
Good Luck with your engine build.
Clois Harlan