Who on the West Coast would you recommend to drill and tap a canted scope mount hole on a M70?
A friend asked me, so I am asking here to get some names.

Hell, I can drill crooked holes with the best of them.

Actually, redrilling an existing hole is tricky because a bit wants to follow the existing hole. It may be better to drill a new hole and modify a scope base to match.

If the hole is cockeyed, you will MILL the hole to the next larger size, then tap. As Uath70 said, a drill will simply follow the existing hole and you end up with the next size larger hole, also crooked.

If the hole is slightly off center or even just canted I have instead made bases drilled to match. This is sometimes to be prefered depending on the situation.

I picked up a real nice FN Commercial that someone had driled & tapped. The holes were all on centerline with the bore, however they all leaned to the right at about 10 degrees. I milled new holes and tapped em to 8-40. Now I have a nice useable rifle. Depending on which bases you use, you may have to alter them for the larger screws.

Question is, is it canted so much that it prevents the scope base from cinching down level? If so, it should be fixed by whatever method. If not, then why bother?

The hole may be able to be straightened by plunging an appropriately size end mill and re-tapping with the tap supported by the spindle to prevent canting. This may or may not work to keep the original screw size. The other way would be to open up to 8-40 screws (using an endmill)but the mounts would need to be opened up too. Everything can be straightened and be on location if the work is done on a mill.

Can't help you with a direct reference but there used to be a guy in the bay area was supposed to do very nice work. Anthony's Precision Rifles.

I just repaired a 1917 action with the holes off center. I abandoned the old holes with screws silver soldered in place and dressed down, then re-drilled the holes on center. The new holes actually lapped partially over into the abandoned ones. All was done on the mill. I have milled out the holes to the next size up many times when centering wasn't an issue.