Twin tachs

One of the tachs in our Aztec has been acting kind of flakey, usually
reading too high when above 2100 rpms, (I've checked it several times with
an optical tach) so I've been contemplating our options of replacing both
tachs with a single dual needle tach. This would open up some panel space
allowing me to spend ludicrous AMU's on another toy.

One option is to simply get a mechanical dual tach and connect both tach
cables to the single tach but I don't know of a dual recording tach that has
dual hour meters. Anybody?

Another option is to get rid of the cables, buy tach generators, and an
electric dual needle tach. But I still don't know of a company that makes a
dual recording tach.

So far, I have not found a company that makes a dual electronic tach.
Neither E.I or Horizon seem to offer a dual tach. Also, due to panel
configuration, I want a 3 1/8" dia tach not the smaller 2 1/4" tachs that EI
or Horizon offer, I have no room for additional 2 1/4" gauges.

Is there anybody out there with any insight into this dilemma?

Thanks,
Jim