Do the math you guys,
before trying to
guess some help for someone.
http://www.classictruckshop.com/garage/shopmathcfm2.php
The formula is as follows: ci x 2 - 15%
or ci x 2 x .85
4.125" Bore: 302 x 2 = 604____604 x .85 = 513.4cfm
4.155" Bore: 306 x 2 = 612____612 x .85 = 520.0cfm
Unless this guy has a huge cam, 600 is too big for a 302.
A stock 302 reguires 513.4cfm___If it's bored .040 over, it is a 306.