5/16" Fuel Pump Inlet for 340?

I have the 6902. Its 15 plus years old and still going. It's been pumping 87E10 it's whole life.

Cam that goes 1800 to 6000? Ima guessing around [email protected]? With X/J heads and 2.02s, Ima guessing power will not touch 400. But let's say it does;
400hp @ .5 pound/hp/ hour =200 pounds/hr.; 200/6pounds per gallon =33 gph. As a streeter you will not likely need much of a pump, cuz top of second gear is already speeding. So your 340 will only be pulling hard for 2 or 3 seconds at a time, but let's say 5 seconds;.
so if she pulls for 5 seconds; thats [33/(60minutes x 60 seconds) ] x 5seconds = .0458 gallons =5.86 ounces. Now up here in Canada a regular can of Coke is 10 ounces. So your 340 will need about 60% of that. But wait there's probably 3 or 4 ounces in the bowls....See the point? Just about any old pump will work under these parameters.
Having said that; stay off the track!! or buy a pump.
IIRC 340s came with 625ish cfm carbs in 68/69
I put a 600 holley on my 360 (400/430hp) for a couple of long distance tours. It ran fine when jetted right. Sure I could feel the power loss in the upper register. But with a 223 cam, it wasn't that lazy around town.
From 5000 to 7000 it runs better with a 750.
She really likes the big TQ. At around 800 total cfm, the top is good to go. And the much smaller primaries keep things sharp down low.

I'm running Eddies and a 230 cam. 10.7Scr, TTIs and an AG intake. 3.55s and a 3.09low M/T.
The M/T really likes the DP Holley
http://www.hughesengines.com/TechArticles/11360dynotestfeb2000.php
http://www.forabodiesonly.com/mopar/showthread.php?t=333502