The X ring is size 012 in buna shore 70, you need an 1/2" end mill and create a Concentric
hole over the 2 shaft holes 0.090 deep. The X ring is .070" cross section, its compressed by both the shaft and OD of the slot so the extra 0.020" depth of the slot takes the side expansion of the X ring.
O ring for the pump outlet the cover seals onto is 1/8" X section, 1/4" ID, 1/2" OD. This replaces the old conical rubber seal.Cover
Take the 5/16 hole the oil pump forces oil into down to the depth of 0.550", check before taking this step that this will not breech the timing cover outer surface. Norton
added a bulge here for the MK3 as there is little extra depth to play with. Use an 5/16 or 8mm end mill as you want the bottom of the hole to be flat for the spring.
The spring I use is the BSA Unit single one, BSA unit single ball check valve spring.
0.6" long 0.25" diameter and wire thickness is 0.015"
Part numbers 40-0381 or 40-0381 or 70-8124 whichever works
Add a 6mm hole at 30 degrees for the OPRV bleed off so the oil goes straight to sump.Crankcase
Also block the crankcase hole the oil dribbles from when you take the timing cover off, its already threaded 1/4" UNC so use a short grub screw, do not screw it in too far, just below the gasket surface.
Not my pic but forgot who's it is to credit them.