Welcome from central Colorado!
I had both those bikes, too! I still have the 750K2, new since 1/1972.
My father-in-law got my 450.
Hello! I'm familiar with ya number of your posts here from having lurked around for a number of months since getting my bike, haha. I've been to Denver once and it seems as though there'd be good riding roads all through Colorado.
¿What happened to your 450 that you couldn't/didn't keep it? Also, ¿how common is/was it to replace the automatic chain oiler gear at the rear of the transmission for these bikes (the 750s)? I ride with member of the SoCal Norton Club/Vincent Owners Group and i've been told ‘it's messy’, though to me it seems very useful and practical.
The 450 was intended to be for my wife. She is a bit timid, though, and the sudden throttle of that big twin spooked her so much she crashed (gently) on her first solo ride in a large parking lot. I probably should have dug around for a 350-ish bike instead (since speed limits at the time were only 55 MPH), but she decided to ride with me and use my back as her bookrest instead. So, on long trips, that's what we did. I had to beef up the suspension on the 750, though: carrying 2-up with full Vetter fairing, heavy detachable (Krauser) bags and a full tourpak with sleeping bags on top wasn't optimum for mountain riding!
That beefed-up suspension was terrific for riding 2-up sans loads in the mountains, though. About 6-7 years ago I had to remove the old Spanish Betor shocks (130k miles on them) and replaced them with some NOS ORCA units: excellent damping, but with progressive 90-120 springs, which are TERRIBLE for 2-up riding. I still have not found some 110 or 120-lb straight-rate springs for them, but hope to: that's what is best.