Welcome. I never found any Canadian block nunbers either and I've looked a long time.
In summary:
261 in Canadian Pontiacs rated 148 hp.
American Corvette 235 w/ 3 carbs, dual exhaust, high lift camshaft,etc rated 150 hp.
As said many times before there's no replacement for displacement. Try to wear out the splash oiler while you build a hot 261. Have fun.
