My comments are assuming you are talking about the upper and lower intake. I'm working off of memory here and will update after a visual.
I have edel rpm and the holes I plugged were the 2 rear ones on top of the lower intake - water jacket and 2 just behind the temperature gauge and heater inlet tube. You need I think 3/8 pipe plugs.

I think at least one came with the intake but you can obtain them from HD, Lowes etc.
The front 2 are for the temperature gauge and the heater tube. The 2 that are just behind the heater tube and temp gauge are not in the water jacket. They need to be plugged also. Then there are 2 at the inlet neck on the upper intake, which edel provide plugs for those. I guess the additional holes can be used for NOs, SC or access to vacuum or something.
Tip: If you intend to use an aftermarket temp. gauge and still want the stock gauge to work, you can put the aftermarket gauge sender unit in the front hole and the stock unit at the rear.
Parts list:
90* fitting for under the upper intake to fit hoses for pcv (eliminates T fitting)
90* fitting for back of upper intake for the other vacuum lines
Oh and remember to put some thread sealant on all the plugs
Peace
Al