Edmonds 8BA Heads Chamber Volume

[1937Coupe]

Hello all, does anyone have data for the chamber size for Edmonds 8BA style aluminum heads? I am helping a fellow flathead enthusiast put a supercharger on his .100 over 239 (stock stroke) flathead. The heads are already on. I saw a post from Ol’Ron from 2011 that said 8:1 on a 239 engine and 8.5:1 on a 255. That data is probably close enough for me but thought I’d ask. Thanks in advance for your help.