Opinions on a 340

For every point rise in compression you will make approx. 3% more power.
More importantly, the larger cam installed will run more efficiently rather than like a lame dog down low.
A lot depends on the intended target of the cars performance and power level sought.

What is it you want to do with the car and how it performs.
(Do not shoot for a HP level as this normally leads to a long list of issues old trying to get a car to perform and be enjoyable for what you want to do with the car.)