Welcome from Chicago! I added Ram Air to my 73 I had in high school. It was not hard at all. I am planning to add it when I get to that point on the 71 that I am currently restoring. I have been buying most of my parts from NPD, and that's where I plan to purchase the ram Air components. As you can see from the pic, I already bought, painted and installed the air cleaner. When I fist bought the car, I purchased some parts from CJ pony parts off the recommendation of the guy I bought the car from. I have had much better experience with NPD as far as quality of parts as well as customer service.
The story behind how I was able to add Ram Air to the 73 as a high school kid was funny. When I was 16 in 1981, I went to a video store with my girl friend and a "older" guy (like 60, doesn't seem so old now, lol) standing at the check out says as we walk in "Nice Mach". I say thanks and he says does it have Ram Air to which I respond "I wish". He says do you want it? I say who doesn't, and he says do you want to be a smart *** or do you want a free Ram Air set up? Turned out he bought a brand new 71 Mach 1 in 71 and it didn't have Ram Air so the dealer ordered him all of the components to add it. The parts came in and he brought them home to install them. That weekend his brother borrowed his car for a date and the brother totaled the car. The new Mach that he bought with the insurance money already had Ram Air so he put all the Ford boxes up in his garage attic for 10 years. He gave me everything for free, the whole set up including hardware and vacuum lines. My girl friend was complaining that he was looking down her shirt at her cleavage and I said let him look he is giving me free Ram air, lol.
As far as radio upgrade, A guy I met at a car show told me about a company called Aurora designs. I am going to look in to sending my factory Ford radio to them to have it upgraded. I heard the radio in this guy's car at a car show and it sound like a high end aftermarket system but he had a factory radio. He said they aren't cheap, but he really was impressed with them and his radio sounded great. You can send your factory radio and they can put blue-tooth and have different packages for a two channel or four channel amps with more power internally in the radio. I think I am going to look at having them do my radio when the resto is done and I am focusing on the non-essentials.