VDC = Direct Current
VAC = Alternating current

Only thing pins are using VAC for as far as lighting goes is GI. Controlled lamps and flashers are always direct current in solid state games.

I agree with not using relays. Just wire them directly, put a molex connector in the middle of the wire harness for your mod (+ease of installation and shopping), respect the flow of electricity in regards to the diodes on the lamp sockets, and you're *fine*...at least with factory. If you have a LED OCD installed, you might have to look a bit deeper because I don't know how much additional current draw the board can put up with. But in general..on System 9 through WPC, you're okay adding a LED wired to a controlled lamp directly...especially if it's already got an LED in there instead of incandescent, and you aren't using the UBER ULTRA RETINA BURNER type.

If using the LED OCD you might need something like the opto isolator to prevent pulling too much additional current, I dunno. I can tell you that when I had Space Shuttle, I direct wired to the controlled lamps in the backglass that are behind the exhaust section that flicker constantly, and had them rigged up to a wire harness that went up to my custom topper and aside from figuring out which way to wire it to prevent interfering with the lamp matrix and causing other inserts to light incorrectly, it was really easy.