Here is how I chose to mount my Zumo 550. I mounted it in 2005 and have had no problems with it.
To mount the Montana the same way you will need the following parts:
These are all Touratech part numbers:
Toutatech 950/990 mounting adapter # 040-06632 $75.20
Garmin Montana mount and power cable # G 11654 $37.99
Touratech locking mount # 065-0600 $184.90
These are the only parts needed to install your gps onto your bike.
The locking feature is a must if you don't want to pull the gps off every time you stop for lunch.
I hooked the power to the accessory power under the dash that is on regardless of the key position. I don't like the gps switching off every time I shut off the bike.
The ram mounts work good but look like an add on instead of something that was made for the bike. Personal preference!