The guy is blowing some smoke at ya, but that's typical for seat of the pants hp numbers.

To get 350 hp from a 327 you'll need to copy the factory L-79 engine of '65-68. See this link, about half way down the page; http://www.yearone.com/enthusiast/re.../momuscle3.htm

Note that your engine has small valve heads, no where near 11 to 1 compression, cast instead of forged pistons, and it's gonna take a 750 cfm carb to work with that stuff. Then there's the cam. The L-79 is pretty radical at 342 degree duration. All that said, the L-79 was a beaut!!