What time of year?
If it's for next spring/summer here's suggestions:
1 - CO-91 to I-70, east to CO-9, north to US-40, east to CO-125, north to CO-14, east to US-287 and in to Fort Collins. It's a beautiful drive
2 - OR...CO-91 to I-70, east to Central City Parkway, north to Central City/Black Hawk, CO-119 north to CO-72, north to CO-7, east to CO-66. east to US-287 then north to Fort Collins. Again another beautiful drive.
3 - FTC to Durango, you could back track #2 above and when in Leadville go south on US-24 to US-285 and continue south to US-285 to US-160 then west to Durango.
4 - OR...alternatively US-287 south from Fort Collins to I-76, west to junction with I-70, west to CO-470, south to US-285 and stay on US-285 all the way to where it intersects US-24, then the remainder of #3 above.
These routes are what Colorado is all about, but best done when the weather is cooperative. IF you're thinking of any time from now onward, all bets are off, it's still doable but you'll need to keep a close eye on the weather and road conditions and maybe plan on the I's if it gets nasty weatherwise.
2007 GMC Sierra SLE 3500HD Dually
2016 Coachmen Catalina Legacy Edition 243RBS
2007 Keystone Outback 25RSS - R.I.P.
