Ok guys, here goes.
Long story... started with NAV II and factory mount on my 04 LT. Switched to SP 2820, and went thru 3 units (all three died). Was using my old NAV II just as a speedometer. Maps woefully out of date.
Then, saw the add for Touratech's package deal for a 665LM AND locking mount. Investigated it pretty thoroughly and noticed that there were four holes in the mount that seemed like they might just match the four holding the factory mount for the NAV II. I called them and talked to a very knowledgable tech who said even if they didn't match exactly, the mount was aluminum and could be drilled to fit. So, I sprang for the package. Not cheap, but I've looked at many other options and the 665LM was the only one I felt was truly viable. I also didn't want to get one that would lose support from Garmin in a year or two. (Side note. I hate Garmin for their pricing, and lack of compassion for my having just purchased a lifetime maps for my last 2820 and when it broke, they weren't supporting in ANY fashion the 2820. Didn't even offer to refund my lifetime maps cost and wouldn't consider moving the license to another unit. Ah, but I digress)
The kit came in, and yesterday, with the help of the Trike dealer in Windsor, CO (NECE, Monty Loftus, p.s. He did all the work) we removed all the skins (Boo BMW for requiring this much effort to get into the top of the bike), removed the old mount and cables, and installed the new mount.
When removing the old cables, the holes between the pass-thrus did not line up and the plastic hole in the top most hole had to be reamed out about 3/4 inch on both sides to allow the new cable to fit thru. We unhooked the old cables from their connectors, used a checker to find the right pins for ground and power, spliced them in, turned on the LT's key and viola', the unit powered up. Then, all that remained was to reinstall all skins, put the unit into the new mount, secure it with the key and come home.
One other note, when removing the old mount, (four metric screws with 2.5 hex heads(metric) lift the grey plastic hood off the actual mount), be careful not to lose the four captive square nuts. they will fall out very easily. they're captive, but only on three sides. There is an open sides on all four. So remove those as soon as you remove the grey plastic hood,
Otherwise, it's really straight forward and looks like it came that way from the factory.