Re: 67 big block cooling
I had a similar problem with my BBC engine. I changed to a 2 row radiator that's the same thickness as the 4 row, but 2 rows give more cooling area. I also changed to a Weiand hi flow aluminum water pump. I don't run a shroud or a electric fan now. I used to have both and ran near 200* traveling, and boiling over after 10-15 minutes of idling.
Now I run 170* driving, and might get to 200* idling in the hottest summer days.
You didn't mention which radiator you have? I also went to the largest I could find (width) as the original was a 19"x 26" core, and the new one is a 19"x31" core.
1971 SS427 Camaro. 2nd owner since 1973!