Avionic Install/Replacement Certification

I have been searching the FAA regulations for information who is authorized
to sign off Com/Nav or avionic equipment installation or replacement. For
now this is hypothetical.

I have 5 years experience in aircraft maintenance from the Air Force and 6
years experience as a radio technician. I hold a valid General Radio
Telephone license but no A&P certification. I have the general knowledge
but am unaware of what authority my FCC license allows and am having trouble
finding the information the regs.

Can someone please tell me what regulations govern certifications
requirements for a avionic sign-off? Based on Part 43, I know radio and
navigation system work is "major" and therefore regulated. I also know if
installing a new radio, an A&P would be required to sign-off any structural
and weight and balance aspects of the install. Does a new radio also
require a second sign-off from an FCC license holder? What about a new ODI
or an GPS?

Again this is hypothetical. At the moment I am toying with the possibility
of pursuing the credentials to become a certified avionic technician.
Thanks.

Dave Salvagnini
2W5 - Maryland