This may be on a tangent but you don't need a Form 1 with a radio, for it to be installable on a G-reg.
An FAA 8103-3 is just fine, if the radio is a new part.
In fact, from digging around a while ago in CAA docs, any paperwork providing
traceability is good enough, but nobody has a financial incentive to tell you that
What you need to do an installation in an ICAO CofA aircraft is Approved Data (e.g. a TSO), which is a different thing from traceability.