chevelle tech

I tried to register my chevelle but it won't let me. Can you help me?

My '68 convertible is finally out of body work, paint and brakes. The factory tach wasn't hooked up when I bought the car (it had an MSD 6 ignition, a knee-knocker tach and after market gauges). I've installed a new MSD 6 AL ignition. Is there any way to get the factory tach to work with the...