Pertronix 600 rev limiter
I'll get you some pictures tomorrow of the install. As for your questions:
I've had it for one month, I did some searching online and didn't see too many bad reviews. I have had problems with MSD and I was nervous about this one. I'm hoping installing it away from engine heat and with a fuse inline will prevent it failing.
Summit has an adapter that they make - I used it and it's just like the mallory version
I mounted it on the firewall to the left of the clutch pedal and routed the wires through the firewall below the ballast resistor. I was able to do this because I removed the fresh air vent that was in the way (I'll get some pictures for you tomorrow).
Differences between it and stock: It idles smoother now, and I have a rev limiter in normal driving and a 2-step for launching. I still have my stock box, ballast resistor and all installed on my car, so if the mallory box fails I can switch plugs from the distributor and coil connections and drive home on the stock electronic ignition set-up (looking under the hood it looks all stock). Your concern about it failing and getting a replacement a month later isn't an issue if you have the stock backup already installed and ready to go.