So have I got this kill switch wiring right?

I found trying to use the Harbour Freight SPST switch confusing too, so we opted for the nicer DPST switch wired like in your "B" example.

And you need two correct?  One on the engine, one in the car?

I can't speak to the longevity of the single pole with the alternator, but it worked fine with the alternator for a few weeks.  Having to run the alternator through some resistor and sink only seems necessary to me if you were looking to  straight ground it and expect it to continue to produce power by the motor turning.  Following the basic principles I know, cutting the circuit won't have that same result as grounding it out, so that wasn't one of my worries.  Maybe I'm ignorant and lucky though. 

I just looked at it as interrupting the two main circuits in the car as close to the source as possible.  I don't know that if you interrupt the battery and alternator circuit, if they're the only two circuits producing current, you'll have to wire the ignition too like your drawing as long as its power supply has been preempted.  I'm sure there are exceptions in some odd cars that people here know about.  I mean, some do choose to run French or British cars with bad electrical history, right?

It worked to run a positive wire from the battery and the output of the alternator into one terminal.  Out of the other terminal you'll be able to run a wire back to the stock alternator output (which would be responsible for returning to the ~14v circuit re-charging the battery) and another to the wire that formerly joined the battery terminal. 

I played with running one or the other through the switch; yes it was necessary to do both because either a well charged battery or an alternator alone would run the car. 

And, Bigds, two switches are required in Chumpcar, so a number of people are wiring both up so they can run that series as well.  Or, they like the idea of the driver having switch access and a switch outside the cockpit for workers.  They're probably the responsible honor student types.  But, only one is required in the rules right now

the drawings that I see have a 2 pole switch with the alternator ckt wired through the 2 small terminals.  The batt is wired through the 2 large terminals.  The alternator ckt breaks first, then the battery ckt.  This is usually necessary on alternators with an external voltage regulator.    I'll try to find the link w/ the drawings, but my computer shit the bed the other day, and my bookmarks disappeared.