383 Rev Limit question

There are several open chamber heads, including the 906s's, 346's, 452's, etc. I mentioned the 452's as they are pretty easy to come up with, and had hardened exhaust seats from the factory. If your 915's are stock, and have the smaller 1.60 exhaust valve, I would expect a small power gain going with any of the open chamber designs, even though you will lose some compression.