gonna throw my opinion in here and throw a twist on the whole thing....I know you already have this 340 however, changing cranks and a bunch of machine work may warrant buying a stroker instead and choosing a little bit higher than stock compression ratio, no replacement for displacement....by the time you weigh in the cost of machine work, pistons and possibly another crank as you indicated, you are very near the cost of a stroker kit and considerably increasing displacement . a mild cam and minor head work would get you near 400hp and keep you within your budget. they are mostly ready to assemble when you get them, look around... here is just one company,
http://www.campbellenterprises.com/...opar-340-360-magnum-stroker-kit.htm#340street