After reading this thread at Honda-tech I just don't know who to believe anymore...

http://www.honda-tech.com/showthread.php?t=717928


PR3 head/B16 Block

STD = 11.643438609136867
.25 OS = 11.703231023151065

PR3 head/B17 Block

STD = 12.193487116069006
.25 OS = 12.256369577319077

PR3 head/B18C Block

STD = 12.58636786521145
.25 OS = 12.649248792586258

P72 head/B18C Block

STD = 12.924594026551906
.25 OS = 12.989047869209281

PR3 head/B18A/B Block

STD = 12.825536009218106
.25 OS = 12.88971493738735

P72 head/B18A/B Block

STD = 13.170743903246784
.25 OS = 13.236528215133324

All calculated using OEM 3 layer gasket @ .026 and the compression height provided by Omniman