The hole in the side of the lifter is the oil supply hole it is fed from the lifter galley oil feeds that you see in the lifter bores in the block. That oil under pressure fills the lifter and then comes out the hole in the top of the lifter where the pushrod sets, oil comes out that hole and travels through the pushrod(pushrod is hollow with hole at each end) and is squirted out onto the rocker fulcrums and valve tips. The orientation of the hole in the lifter does not matter, that hole is posistioned in a groove that goes all the way around the lifter so that entire groove is filled with oil under pressure as long as the engine is running so it does not matter where the hole is facing.
The only time reusing used valvetrain components is acceptable is they must be in good working condition and they MUST be returned to there original place they were removed from.
Example:
1. When reusing good lifters they MUST be returned to the original lifter bore they were removed from.
2. Pushrods MUST be returned to the original lifter and rocker arm and the ends of the pushrods MUST be returned to there proper orientation, in other words the end that was working the rocker arm MUST be returned to that rocker arm and the end that was being worked by the lifter MUST be returned to THAT lifter it originaly came from.
3. The rocker arm fulcrums MUST be reinstalled to the original rocker arm it came from and orientated properly as well.
4. Used rocker arms MUST be returned to the original posistion(IE cylinder and valve it came from during teardown.
By now you're probably saying to yourself WHAT DOES IT MATTER?
Well all those parts wear into each other and establish wear patterns that are unique to each set of components.(kinda like your fingerprints, no 2 are exactaly the same) Now with all new components the orientation does not matter because wear patterns have not been established yet.
When using used components and you do not return EVERYTHING to its original posistion accelerated wear of those components will happen because the wear patterns do not match and very soon the valvetrain will be loose and sloppy and continued use will DESTROY the components in qeustion.
I have seen lifters and cam lobes eaten all to pieces because the original lifter(when using used lifters) was not returned to the original lifter bore it came from. Same goes for the pushrods,rocker arms and rocker arm fulcrums.
I hope when you disassembled the engine you marked what parts came from where and you returned them to the original places, if not I HIGHLY recomend you replace all those parts with new parts because if you dont you will be tearing into the engine again to replace them and possably the camshaft as well within 5,000 miles or so give or take 2,000 miles.