best carb for 340?

Someone mention that a TQ isn't a race carb?
This would be slightly incorrect since it was designed and developed as a race carb making its intro in NASCAR (IIRC) a few years before it was standard equipment on passenger cars. The smaller primary side is not a hinderance.

You do not want the first year TQ. Less emissions equipment on it the better for high performance useage.

Theres a few draw backs to a TQ. Rods can be made from AFB/AVS (Edelbrock) rods but jets, front and rear are not available. (Though *I think* someone is making the front jets.
The rebuilding of one, may require bushing the shafts. Break the main body, you could be SOL! The carbs centers do not readily swap with another. You must also use the correct gaskets for that carb you have.
And the last draw back is the huge secondary side which will require an adapter for square ore intakes. Unless you can carve up the intake to accept a TQ. The Weiand Stealth and Edelbrocks LD340 can be cut up to take a TQ.

What is nice though is that the Edelbrock performer, the Action plus and MoPars M1 single plane will take a TQ on no problem. Also the seldom seen Offenhauser Port-O-Sonic can take a TQ, IF it is the right Intake. The do come with a square bore as well. Excellent intake with MoPars mods!