I wonder if there is an aftermarket one that fits the original bracket that's looks ok.
I haven't tried it but I did buy a 65 tach for cheap that doesn't work and just haven't got around to try to fit another tach into the chrome bezel.
I did this maybe 15 years ago for a friend with a 65 'cuda who was looking for a tach... I "Think" it was a Stewart Warner gauge I fitted to the correct cuda 65 Bezel...
In the bottom picture I'm testing it with jumper wires to my 65 'cuda... These newer tachs do not need the Sardine can (sending unit)...