Burnt some Spaghetti!

This is based on one of the B-body versions of the heavy duty alternator wiring, and its pretty simple.
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The terminal junction isn't neccessary, but does make a nice location to tap power for headlight relays and/or an MSD ignition.
Iff there are no high draw accessories (such as a defroster grid) I'd probably go with 10 and 12 gage wire rather than 8 and 10. Much easier to make good connections, less chance of problems with support and room.