The 4 larger bolt holes are only drilled on heads that originally came equipped with EFI; same with the notches.
It's not super difficult to modify your existing head while it's still on the car. I did it to my e88 when I switched to megasquirt. The hardest part is the bolt holes. I used an old head I had laying around as a guide for those. It's very important to take off the valve cover and measure how thick the head is at the point where you are going to drill, because the later heads were made thicker where the holes go, but the early heads were not. The two outer ones can be fairly deep, but the two center ones can not be very deep at all (see first picture). I covered all the ports with duct tape to keep shavings out.
For the notches, use a cylindrical rotary rasp to carve them out, they work great. I put a nissan gasket up to the head (didn't trust felpro's placing) and colored all of the material that was exposed with a red paint marker. Then I held the drill at about a 45 degree angle and carved the notch out until all the paint was gone. It is important to keep anything that doesn't like aluminum shavings completely covered, as this is very messy. To help minimize the mess, I had a friend hold the vacuum cleaner hose as close to the rasp as possible to suck up most of the shavings as soon as they came off the head. I kept every port covered with duct tape except the port I was working on, which I stuffed tight with 3 or 4 shop towels. I vacuumed all the shavings up before I removed the towels.