Congrats on the Mallory. Which one did you end up getting? Also, have you been keeping track of your milage in the past? I'd be interested to see what kind of gains you will be getting.
Upgrading the coil over the stock unit should provide a hotter spark, just remember to use Mallory's suggestion for the plug gap, since you'll be able to run it more open. I know they recently released a newer coil that has the ballast resistor built-into the coil. Good if using just the unilite, but you can't use that version with the Hyfire.
For the Hyfire, from what I've been getting, it's simply a digitally controlled box that does the same thing as the MSD ignition box at a cheaper price. The Megasquirt forums really bash the MSD as being overpriced and a nearly empty circuit board. Because of the multiple spark nature, you definitely can't just run a wire to the coil terminal like it's set up now. Otherwise, you'll be giving the ECU a confusing mess of multiple sparks per cylinder. You would need a clean tach signal for the fuel computer to use.
At higher RPM it ends up being a single long spark per firing, which is probably why people running high RPM have less troubles. But I would definitely plan on having to run the tach adapter.
My oil line fix
My 100k stopped odometer fix
Brace for impact, I'm in a "modifying mood". Massive thread count inbound.