The pertronix you can get most anywhere. i bought mine from mustangs plus (mustangsplus.com) as I was at thier shop for a show. Most of the other parts vendors carry them now.
It depends on how you want to build a ram air setup. You really can't get a kit, its more of a build it your self type thing. either A) a hood with a scoop (like the shelby style) and a tall air filter with a K&N extreme air cleaner top. That's easy but costly..
b) use a closed breather and route tubing somewhere on the front of the car. Much harder since most stuff is in the way...
Your other option is trying to pick up air at the base of the windshield (like a cowl hood is designed to do).
HTH
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Marcus
68 Mustang giggling 351C coming soon