My SGJ came with a 490T in the bridge position and I was looking to swap it out with another pickup I have lying around. Only thing is, I've never worked with these Gibson wiring harnesses with the plug in connections before. The 490T connector has a bare, green, white, black and red wire while the V8 I'm putting in only has a bare, red and white, the last of which I understand is only for coil tapping, which I won't do. I tried connecting the bares and reds and am getting no signal whatsoever.

If the V8 (Ibanez?) only has three wires, then it can't be split. At a guess, I'd say that your bare and white should be soldered together and to the ground (bare will be ground, white will be south start). That just leaves red to be your hot.

So, solder the red to where the Gibson red was, then the bare and white to where the black and bare were.