"Restricted" doesn't mean jack. It's a Colt so it was built in the US so 922r doesn't apply. Modify to your heart's content. Do yourself a favor though and spring for quality accessories. You have a good quality rifle, no point in covering it in Tapco stuff and putting a $40 red dot on top. Magpul makes good stuff and they aren't very expensive.
I don't collect guns, I accumulate them.