340 on dyno video, whats your opinion

I'll give you the first. Depending on the specifics, it may need more time to be fully run in, but its a still good and any leaks or problems can be addressed.
On the second, eh. We've seen guys here post all sorts of dyno Hp results. You'll have an idea of what it can make, if you can get all the specifics like rate of acceleration, and correction method. I think the real advantage is if you can spend even a bit of time (and money) on tuning the combo; or at minimum at least getting the timing and AFR through the rpms so you have a ballpark starting point.