fuel line size

[JUSTANOVA]

i have come to the guru's for a fuel line size recommendation from the tank to the pump and maybe a mech. pump recommendation.

the car is a 1970 chev. impala with a 700r4/2500 stall. 355 rear gears and a 26"tall tire.

the car was originally a smallblock car and it still has the small 5/16" fuel line from the tank and no return line. from what i have read, all the factory big block cars had a 3/8" line. will the 3/8" line from the tank to the pump be able to flow enough fuel to support the eng. listed below? and should I run a return line also? it also has a stock replacement style mechanical pump on it too.

the engine when driving the car hard will fall flat on its face at about 4700-5000 rpms and if you back slightly out of the gas it will catch back up for a second but still doesnt seem to pull on the top end like it should.

also if anyone wants to take a stab at a horsepower est. please be my guest.

eng. specs
402 big block
9.0:1 compression
stock closed chamber oval port heads
edelbrock performer that was gasket matched to heads
jet performance q-jet
comp cams camshaft see specs below. with recommended valve springs and degreed in per comps recommendation
comp 1.7 roller tip rockers
stock exhuast manifolds for now but headers may be in the near future.
2.5" dual exhaust through thrush turbo style mufflers out the back under the bumper. (non mandrel bent)
mallory ready to run HEI distributor with msd wires.

Part Number11-670-4

Grind Number CB NOSATLGIA LS-6H+

Gross Valve Lift0.53 0.524


Duration At 0.006 Tappet Lift276 283

These Specs Are For The Cam Installed At 108 Intake CL


Duration At 0.05 229 236


Lobe Lift0.312 0.308


Lobe Separation112



sorry for the long post but I wanted you guys to have as much info as possible.

[malibu795]

get the 5/16" line out of there you need more fuel than it can supply with easy.

3/8" line @ ~7-10psi is good for ~550-600hp

all the lines on my gasser vehicles have been 3/8"