I'm not a machinist, but:
* I'd suggest knurling the intake guides as well to insure proper, consistent clearances and better lubrication.
* Exhaust clearance is normally more than intake, but I don't know the numbers.
* Single groove keepers are easier to find and can be made from better materials - better for performance applications. (Machined locks are better than stamped.) Valve choice determines lock grooves.
* Stainless valves because they are better, inexpensive enough and tend to have a "nail-head" design, which is better for flow on the intake side over the OEM "tulip" style.
* Be careful with "mixing" intake & exhaust valve brands. Best to stay consistent with brands for quality, lock style & valve length.
Be careful with the "bigger" plans related to rpm's, cam, intake & porting. Bigger isn't always better. Some dual plane intakes perform better than some single planes.