When running 2 fuel pumps, like 2 Holley black pumps, do you connect them in series (on one line) or have them each on their own dedicated fuel line?

67 Barracuda street car, 408, e85, 1.38 60', 6.44 @105.9 in the 1/8 mile, 10.19 @130.5 in the 1/4...so far....