~450hp from stock stroke 340?

Why is 450 the goal and how will you know if you meet it? Will the engine be dyno'd? Whether or not you get there is beside the point for me. It should be a kickass combo regardless.
First time building an engine, will probably get it dynoed at some point. I’m using very basic preliminaries (my butt dyno). It will be a very dramatic change to what I have now.

Stock small valve J heads, ld340 intake, 670 street avenger, slightly bigger cam than stock.