The tach was included with the K and S code 4 speeds, not requiring a separate cost option. I don't think that was the case for T, C, and A codes.
+1
and the 8K tachs I know were on the K-codes w/4 speeds, I'd have to research other applications besides Shelby's.
Otherwise, the RPO setup was typically seen as the 6K tach. Seen several over the years on unrestored C-codes, A-codes and S-codes, most were auto trans cars though.
I've seen one unrestored K-code fastback GTA's without the tach