I meant the fitting that Rusty was referring to, which is a 5/16" inverted flare, like a stock fitting that will go right in the Edelbrock threads. You don't have to use the 3/8" hose barb, and since you have a 5/16" line already from the pump, it seems to us to make more sense to get the adapter and keep it 5/16" all the way through. The parts I posted a picture of are what you could use, and I don't need them.
Your fuel pump isn't an NPT connector, it is an inverted flare. If you want to use the Edelbrock parts you bought, you would need a 5/16" inverted flare to 6 AN adapter; something like this, I think
http://www.jegs.com/i/Earl's/361/961946/10002/-1.