See post #8 We discuss cams for 318's here a lot. Try "318 cam" in the search box and read through the posts. It's easy to over-cam a small cube engine. I like to use the 220° @ .050 as a guideline for 318 cams in street applications. Yes your better manifolds, dual exhaust , 4 barrel, and 3:55 gears are definitely a plus. You can go bigger if you use a higher stall converter. That will make up for the rougher idle at a higher rpm. That's where big duration cams have issues.
