The side oiler oils the rods & mains first then the top of the engine ie valve train.
The regular FE like a 390 or 428
oil the top of the engine first and the rods and mains last and that what has caused many bearing failures at higher RPM.
Also the FE mains are drilled so that once a bearing is installed there can be as much as half the
oil hole not matching the hole in the bearing and all FEs should have the
oil openings opened up to get full lubricaion to the main bearings.