I'm installing a MSD6AL in my 67. Will the factory tach work or do I need the Adapter they talk about in the instructions.

Just wire your factory tach into the 'tach output' port on the box.

I just installed the 6AL in my '69 and the factory tach would not work without the adapter. Although...the guy on the MSD tech line told me it would....it still wouldn't until i installed the adapter. go figure.

You need the tach adapter from MSD (at least my 69 did).

Jody