[68 P.O.S.]

It all depends on how involved you want to get into the wiring, but the easiest thing to do is get OEM style harnesses from either M&H or AAW. You can piece meal sections like you're thinking and they'll work with the existing wiring. Also, M&H and AAW both offer OEM harnesses with upgrades too, like wiring for HEI, electric choke, voltmeter, internally regulated alternator, and light relays. And they come all wrapped up, so 100% plug n play.