I believe Fisher Body used the same cutout for all '68 floor shifts - I can find no difference/dimensions in the AIM.
The shifter appears to be an aftermarket (bolt stops) Competition Plus four speed shifter, non-console for general use - could have been used on a lot of things. Floor hasn't been butchered too awfully bad - imminently repairable. Couple of options for shifters, from retrofit with a Muncie handle to a reproduction Muncie shifter, depending on what you want to create.
Regards -