Interesting request. There are some folks I will not even let near my porting bench because I spent 30 years learning how to port heads and intakes. I have invested thousands of dollars learning the skill. Others have spent thousands on buying their ported heads and intakes.
...........Now with that said.........
Scribe the gasket opening onto the intake manifold flange. You can use machinists dye or a Sharpie pen to "blue" the flange so you can see where you scribe. If you look closely at the flange you can see the imprint left from the gasket to get reference to its placement. Now buy about $450 in porting tools (if you dont already have them). Then carefully open the ports out to the scribed lines but leave about. 020" smaller all theq way around the port opening. Then move your way up the entire port. Bell mouth the inlet to each port as best as you can. Use non ferrous 6" carbide cutters. Have a big wax candle on your bench to dip the cutter into to help prevent clogging the cutter flutes. Make the port walls as straight as you can. Air doesn't like to make turns or bumps. Remove the injector boss out of the ports, too. If you use a FelPro 1200 gasket you WILL have to break out the JB Weld to fill a hole or two. Are you matching to a ported head or stock head. If you have stock heads you are wasting your time. (Unless this is a learning momemt) Good luck. It's a tough way to gain a little power. After you are finished let me know if you will EVER attempt it again. Most guys that I have shown the basics to say they will NEVER.....NOT EVER do that again. Dirty work. Think safety too. Hearing protection, face shield, and a dust mask. You will need a box of sanding rolls too, along with a 6" mandrel and a router controller to turn the speed of your die grinder down. If you are planning on using an air grinder add gloves to the mix, too. You'll freeze your hands to the tool in short order. Have at it and if you have any specific questions ask. I would suggest you read a ton of info before you start. You have to become a student of airflow before you grind on a set of heads. I did my first set back in 1979. I feel dumber now than I did back then. David Vizard has books out that will get you in the right direction. Go to a machine shop and run your fingers into every ported head and intake you can. Try and "see" the air moving through the ports. Take a spoon the the kitchen sink with the faucet at a slow stream. Move the spoon around in the water stream and watch the water move around. Air does the same thing. Hope this helps.