77 or 78 tach?

[77BBGMC]

I purchased a tach cluster several months ago and finally put it in this weekend. I had to do a search to clarify a few things on the tach, I read somewhere that the clusters for 76 and 77 were the same. Looking at the pictures it looked like the cluster I installed was from a 78?? It was pretty much a plug and go set up (except for wiring the tach). Everything works except for the high beams and the temp gauge, the other temp gauge didn't work either (project for another day).

Looking at the picture can you tell what year of tach this is?

Disregard the makeshift bezel, the original was in bad shape so I found one off a 79 and painted it to get me by until interior restoration.

Thx!