Ok, I searched the forums, but am still confused. I have a 69 Malibu, 69 SS frame, and a 427 engine. The frame has 2 fuel lines running. The original tank/sending unit has but 1. Do I need to run a return for the 427, or would a single be sufficient. Not running an electric, yet, but want to be able to if that comes around. If I need to run a return, can just the sending unit be replaced?

Thanks!!:beers:

Factory sending units had either one or two lines. The second line (on those with two) is for the "vapor return" or bleed line which is usually 1/4". This line is used to circulate a small amount of fuel back to the tank to reduce vapor lock. This is NOT the same as an electric pump with a return regulator where ALL of the unused fuel is returned to the tank. If you want to use a return regulator you will need a bigger return line and a sending unit with a bigger return such as:

http://www.robbmcperformance.com/products/1069_gmsend.html