I have a 71 chevelle 402 BB It's a totally original car with a perked up original engine. I have the dual line factory fuel pump. It's going bad. What performance fuel pump should I buy and what do I do with the other fuel line?? I don't think the replacement performance fuel pumps have two lines?

Just get the stock pump. Unless you're over 600 HP, it'll be fine.

You'll actually get noticeable high-RPM results from a lightweight pump rod such as a Moroso. That's the upgrade I'd suggest, rather than a pump that doesn't fit your car.

So stock pump but a light weight rod?
The stock pump has enough psi for a 366 hp motor?

Right.

The stock pump seems to work fine up to at least 500 HP, probably well beyond that.

Most often, if you have fuel delivery issues, it's not the pump; one of the most common causes is crusties built up in the pickup tube in the gas tank. That is a problem especially in cars that have sat around alot.

I believe Jacson Racing has an upgraded In-Tank fuel pump for justabout any application. I run 2 of them in my Malibu...1 for the fuel system and 1 for the standalone nitrous plate shot set up.