Some info from that I found here from a 10 year old post:
"Improve oiling? You know, there's just not a lot that really needs to be done to a Pontiac to improve oiling for street performance. Plenty of very strong Pontiacs running around out there with the oiling systems just as the engineers designed them.
That said, there are a few things you can do that certainly won't hurt.
First - remove all the casting flash in the oil drainbacks in the heads and around the lifter bores in the block. That will help oil drain back to the pan.
Second, modify the main bearing oil feed holes. If you look at the holes in the main bearings you'll notice they are significantly smaller than the holes in the block. The easiest thing to do is to take a small rat-tail file and lengthen the oil hole in the bearing along the groove until it's just as wide as the oil hole recess in the block.
If you're really brave, and prepared to do even more work, you can drill holes in the bearings to match the location and size of the holes in the block, but I feel this is overkill. That didn't stop me from trying it once though -
http://misc.willbaker.com/440engine/drilledmains.jpg
The reason the larger holes are offset some from the original holes in the bearings is because the original oil holes in the bearings are inline with the passages in the block that feed the cam bearings. The feed passages to the main bearings come down from the passenger side lifter galley at an angle, so I drilled new holes to be inline with the actual feed passages in the block. Like I said, this is overkill for a street engine. If you really feel like messing with this, elongating the holes with a file as mentioned above will get the job done. Be sure to thoroughly debur the bearing shell when you're done.
Third - block off the bypass valve in your oil filter adapter. Remove the small screw, spring, checkball and valve itself then either drive a small core plug in and stake it in place or tap the hole and insert a small pipe plug. If you keep your oil changed and use a quality filter you don't need or want that bypass there.
Fourth - thoroughly inspect your oil pump. This should be done on ANY new oil pump but I'm surprised at how many people feel they're fine to install right out of the box. Disassemble the pump and clean it thoroughly to remove any debris that might be present, especially around the check ball. Check the depth of the gears to the base of the pump, you don't want more than .003".
Fifth - chamfer the oil input hole in the block where the pump bolts up so that any small misalignment of the pump output hole to the block input hole won't present a restriction. On most pumps I've seen, the passage to the block through the pump body is cast, not drilled and not always round. You can also run a drill through this passage while you've got the pump apart to remove any restriction to flow imparted by the roughness or out-of-roundness of the casting.
That's about all I can think of for now. As mentioned, for a 99.99% street engine this is just about all unnecessary, but if you're like me, you do it anyway just to say you did..."