When I was in need of a new firing tool the GBs were not "in stock" so I don't know exactly what i may be missing, but I went the way of the Pertronix. It was about $75 and only took an hour to install, would have been less but there was an extra wire from the ignition that I wasn't sure what to do with and I had to post and wait to hear from the list. (What an awesome group, there is no way I would have bought a car without lurking for a month or so and seeing all of the available info.)
After I timed it, the car sounded better than ever, ran better than ever, and shortened my "warm up" time to almost nothing. I'm running a stock 1600 and can appreciate go fast goodies but i've been really happy.
Flame away, Booners!
Eddie