Hey drego,
My project is a '65 coupe, 289. My combustion chambers are rated from 55-58 cc's from the numbers I've seen. Your '67 motor will likely have a little bit bigger chambers, but those 75 heads are smog era and probably have pretty big chambers. So while your head might flow more with those bigger valves, your static compression would be way too low to take advantage of it.
Of course this is my opinion from stuff I've read, and I could be missing something. Everybody feel free to correct me.