As I’m sure you know, the factory tilt wheel option on ‘64 Avantis is quite rare.
That same tilt mechanism is more commonly found in early ‘A’ series Avanti ll’s.
I’ve never worked on one, but I think that GM used the same unit in mid sixties Buicks, Olds, Chevy, etc.
I’d guess that if you can source a shop manual for one of those vehicles it would give you the info you need in depth… Good luck!