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.
'91 Toyota Pickup
'09 Kawasaki KLR650
'12 Gunnar Rockhound 29
"To live is to suffer, to survive is to find some meaning in the suffering." -- Friedrich Nietzsche