I've got the RT USB-81, which will work for firmware upgrades.
I also have the RT Systems programming software.
FWIW, I also the GTRANS cable and built a DIN8 to DB9 adapter if anyone wants to try GPS in, waypoints out of their FTM-350. It works with various devices and I've tested it with a Nuvi 350 and a GPS-18.
"Silent enim leges inter arma." -- Cicero