Best head/cam combo for a 340?

What are you putting the motor in? What is your plans for the car?

If it is a street car....
If you don't aready have heads, I would look for a set of later design swirl port heads or even consider putting a set of Magnum heads on it.

I did a motor years ago for my dads 68 barracuda. I used a stock 70 model bottom end build with KB flat tops keeping compression around 10:1, took a set of J-heads and opened the valves up to 2.02/1.60 and had a really good valve job done, no porting. Used a Comp Cams XE268, RPM intake, 750 Carb, electronic ignition and a set of headers. It was a 904 with an MP166K converter and 3.55 gears. The car was very streetable and ran awesome......