Help with reverse lights...

So, I don't have reverse lights in my 69 Valiant. Installed a 727 and 408 stroker. Was a column shift, but I installed a Hurst Promatic. I thought there wasn't anything I needed to do and that the switch in the trans would still work when I shifted into reverse. What should I check? Bulbs work, 3 prong plug is on the switch on the trans... Is there a way to test the switch? I've heard discussion about rooster combs, but know nothing about them. Any suggestions on where to start trouble shooting would be greatly appreciated.