'68 318 to carbed Magnum 5.2: Check my checklist

I would be tempted to hit the buy it now button for that price, but check which fitting you have on the carb. I don't have a carter or eldebrock here to tell you what thread size.

It takes an adapter which apparently exists, so I'm not too concerned:
http://www.moparaction.com/Article/Zinger/1.jpg

-Kurt