There are eight holes to drill, however if you don’t want a tac rail, then it would be five, and if you are using a standard Ruger barrel, then you would not need the pin alignment hole.
Drill List: :
5/16 (take down lever hole)
1/8 (ejector mounting screw hole)
9/64 (slot locator hole for slide stop bottom cutout relief)
#39 (ejector tab hole)
#31 (6-48 tap holes)