head casting number 4772576?

Myron,
All heads that I flow are at 28", as this is the standard for the industry.
heres a ported 308 with a 1.88 valve, I didn't flow the exh. as I was only interested in the int. flow. The heads that are previously posted are out of the box and not ported.

ported 308 w/1.88
lift int.
.100 80
.200 172
.300 216
.400 239
.500 248
.600 247

stock W-2 w/2.02/1.60
lift Int/exh.
.200 104/91
.300 157/133
.400 206/153
.500 247/172
.600 241/182
.700 235/185

stock 915 w/2.02/1.60
lift int/exh
.100 84/79
.200 138/121
.300 199/148
.400 218/149
.500 225/153
.600 219/155
.700 220/155

You can also find other heads that I flowed on the cylinder heads 101 thread, and they cover a wider selection with different modifications done to them. The flows that I'm posting here are the closest to what you've ask for.
What is the whole casting # on your 576 heads?
These heads haven't ever been milled to my knowledge, and the valves that I use are from mopar as they will flow better than the aftermarket stuff, and also being made by Ferrea are a high quality valve.
As for compairing these heads to the 308's we might as well be talking about 318's and 360's as theres that much difference in them. These resemble a aluminum race head more than a stock iron head, I've seen alot of iron heads and haven't seen stock set look like this. Physically they look the same from the out side, but the ports are very different. Also from a tulip intake valve and a nail head there can be as much as 8 cc's lost or gained depending on which way your going. And what manufacture that is used.