What 340 camshaft?

Most anything up to about 240 @ .050 will work......though that's gettin "a little big" for something to drive on the street a lot. The one I recommended is part of the DEH grind series. That's dual energy hydraulic. They are old school grinds, but they are modern at the same time. You get the specs of the Thumpr and Whiplash without the price tag. Look at the large duration split. Just like a Whiplash or Thumpr. But ground on a 110, so vacuum signal and street manners will be a little better. That series is way over looked for other lines that have snappy names, but they are a very good line of camshafts.

But most of these that have been suggested are good. Just pick one and go. You can drive yourself crazy. They'll all make "about" the same power unless you over cam it badly or use one that's too small.
Most up to the .557 were all designed around the pass car heads, so you're absolutely right on the "up to 240" and even then if you keep the ratio ..they perform.