Aren't the 4 gage wires the two primary battery cables? OE battery cables are 6 gage or so, so I am assuming you have two big fat cables from the battery.
If that is the case, the black (ground, battery negative) hooks to the engine; on a 69 small block car, the battery main ground went to the upper rear alternator bracket bolt, where it attaches to the intake manifold.
The battery positive runs down along the oil pan rail, connecting to the big center lug on the starter solenoid.
As Ev mentioned, the 12V feed to the distributor should go to the 'Bat" terminal on the distributor; if your cap is labeled with + and - instead of "bat" and "tach", the 12V feed goes to the +, and the tach would go to -.
Best thing to do at this point is use the diagrams on this link ( https://www.camaros.net/forums/showthread.php?t=93576
; you'll have to PM JimM for a password) and understand how GM wired the 69 originally, then look at the Painless diagrams and go from there.
The feed for the distributor should come right from the firewall connector; the OE harness had a yellow wire from the starter R terminal to the coil, which provided a full 12V to the points when the starter was engaged. You don't need that with HEI.
The only things connected to the starter should be the hot wire (GM color purple, 12 gage) to the S terminal, the big thick battery lead to the B terminal (biggest terminal), and possibly the alternator charging lead (I'm not sure how Painless charges the battery; my AAW kit put the charging wire on the starter solenoid with the battery cable, instead of using the junction block behind the battery like OE).