Flow is a whole separate issue. I mean that they won't go into choke on your typical 383 until just below that. Where it peaks depends on other things but I'd aim for peaking a little below your redline. Peak is sort of irrelevant though as you want the highest average powers through the strip, many engines don't fall off before redline and that may be perfectly okay if it nets you more average power. It's all in the curve.
210cc heads are typically a good choice for a hot street sbc.