The only options you have are:
1. Corvette radio '68-'76
2. custom radio design, such as those available from many Corvette vendors
like Mid America, Eckler's, etc.
3. Cutting the dash to fit a modern radio
Here is another option if you might want, to keep the original look of your
dash but have a modern audio unit.
This company will take your original unit and replace the innards with a 180
watt digital stereo receiver with connectability for a remote CD changer and
XM radio. The unit retains and uses all of the original knobs and buttons.
Cost for the conversion, $399.
I plan to go this route to replace the POS Custom auto sound unit in my '65.
Does anyone have a clean non-working stereo for a '65 that they would like
to get rid of?