California Bill Fisher's 1955 GMC speed manual says it is safe to go to 4.125. At .080 you have .045 left for another bore. They actually made 302 pistons up to 4.1875. That is pushing it. You should try to locate a copy of this little book. It has way more 302 info than the '54 edition of the Chevrolet, GMC, & Buick Speed Manual.
