The slots I think you are referring to are to place a screwdriver or a drift against to knock the tappet guide free of its taper. It does not break through to the bore and so is not a oiling feature. So they should face the timing cover, except the one at the lower rear. That one has to face downward at an angle due to being blocked by the supporting casting. Again, align so as to afford the best purchase with a drift for knowing out.
Oops, just noticed in your pictures you have an additional slot. Not sure if that is original, or a modification. Presumably it should go up to introduce oil. Problem is the same lower rear tappet guide mentioned before is blocked by the casting for the slot to be any use. There should be several small holes between the timing chest that the tappet chests. A larger hole part way up to allow oil mist into the tappet chest to oil the valve stems. Then a smaller hole to drain oil back from the tappet chest to he timing chest. So if it has those holes, no reason to have the slot in the tappet guided facing downward to drain out excess oil. Unless they found too much oil was going into the tappet chests...
-Doug
