Just a few hints.
First, the wire colors you mentioned are correct. also, use the larger violet wire for the start wire.
You didn't mention the brake wire, but it is blk/red.
I used the tachless method. I try to not do anything that will keep my car from running. If the wire from the coil to the inside of the car shorts out, the car stops. The tachless method doesn't effect the ign system.
The last recommendation is if the car has a factory alarm system (even if it doesnt work) you can run the 4 wires from the ign switch to the passenger side kick panel. Mount the unit there and then you can get most if the other signals you need from the alarm system. Forinstance, stop lights, hood pin switch (br\wt\gy), interior lights (br/wt/blk), parking lamp (gy/wt), door lock/unlock (blue). Makes installation easy.
Let me know if you need more information.

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84 500 SEL (307,xxx miles)