cam clearances

Due to the complex angles of the lifters to pushrods to rocker arms on a small block your .470 lift cam will only have about .450 lift at the valve, and that's with perfect geometry. Even with that said you need to actually measure your heads capabilities because they can vary a lot. I've measured some that bind up at .450 lift and others that will handle .500 lift before binding. Factory specs were far and wide. No valve reliefs in the pistons is the only thing I can say that shouldn't be a problem.

As for the cams, I can't fairly compare them by the information you've given. The advertised duration means little. Duration at .050" is the specification to compare by. IMO both cams are way too big for a 318 that "really" has only about 7.5~8 to 1 compression. It'll be a dog on take off with a cam that big. Yeah it'll sound nasty but when you get outran by some mom in her soccer van it'll sure be embarrassing. Gas mileage will be bad too as will cold starts