Hi and welcome to MedHelp.
C1 to T1? that seems like a bit much......but I do know of a few that have had fusions and can drive, but not sure the amount of disks fused are the same....but to drive extended rear view mirrors were added since ROM is limited. ( like for towing a travel trailer.)
I am sure there are groups out there....all depends on the reason a fusion was necessary, that could be where to go for support...IE- my friend also has Chiari, EDS, POTS, ....EDS was the reason for fusion so EDS communities are the best for her for fusion support.