Yes, the wire harness from the small clock goes over to the area where your big clock is. I'm pretty sure it plugs into the back of the tach.

So that makes this the perfect time to put a tach in your car!

HOWEVER there's no reason you can't wire up the small clock to run, without a tach.

You'll need to hook up the 3 leads where they need to go. One is ground. One is constant power for the clock. The other is dimmed power to light up the clock. A match held up in front of it might provide more light but would be less safe. I'm serious. You could make a case for not bothering to wire the light. If it's dark, you should be home by now!

I believe the bottom end of the fuse panel is where the constant power is. You'll see - where the power door locks and dome light and brake light are. The upper end is switched, powered only when key is turned.

I can't tell you offhand exactly which wire at the dimmer is the input and output but you can figure it out with an electrical tester. Definitely don't wire the clock lamp to be always lit because that will drain your battery.
--
Sven: '89 245 NA, 951 ECU, expanded air dam, forward belly pan reaches oem belly pan, airbox heater upgraded, E-fan, 205/65-15 at 50 psi, IPD sways, no a/c-p/s belt, E-Codes, amber front corner reflectors, aero front face, quad horns, tach, small clock.