Garmin, TruTrak and (I am pretty sure) GRT are all interchangeable with regards to brackets (not wiring). I haven't used Dynon, Trio, or MGL servos, so I can't comment on those.
Paul F. Dye
Editor at Large - KITPLANES Magazine
RV-8 - N188PD
RV-6 (By Marriage) - N164MS - "Mikey"
RV-3B - N13PL - "Tsamsiyu"
A&P, EAA Tech Counselor/Flight Advisor
Dayton Valley Airpark (A34)