After talking to James Larrowe about a 261 he has, he told me that the 235 head will raise the compression 1/2 a point to around 7.75:1. This was a common swap on trucks used at higher altitudes.
'45 Ford PU 66 Valiant wagon, leaning tower of power. 79 Chevy C10 w/250 02 PT Cruiser Convertable