$250 for a stock forged crank that still needs machining??? Holy crap that's high! You ought to be able to find one cheaper than that!
Realistically, I think a cast may be fine for what you want to do, but I'd rather see a forged crank in a motor making that much power. You've already spent good money on a girdle, studs, etc. Get a forged crank and don't worry about it.
CHIP
'70 hemicuda, 575" Hemi, 727, Dana 60
'69 road runner, 440-6, 18 spline 4 speed, Dana 60
'71 Demon, 340, low gear 904, 8.75
'73 Chrysler New Yorker, 440, 727, 8.75
'90 Chevy 454SS Silverado, 476" BBC, TH400, 14 bolt
'06 GMC 2500HD LBZ Duramax
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