What car is this going in, what's the weight, trans/converter (/clutch), rear gearing, and is there any chassis work done?
450
honest flywheel HP will easily put a well-prepared 3500 lb car solidly into the 11's w/o breaking a sweat, and pushing 450 HP from a 396 is about as difficult as falling off a log. Unless you have your heart set on it, you don't need to bother with the added expense of a roller cam & lifters, a relatively mild flat tappet will easily do the job.
3/8" rods will be more than adequate with a good set of bolts and the obligatory prep work. The engine should be able to turn 6500+ until the cows come home.
Of the two intakes you mentioned, the C427X would be the better choice, and even that's going to be down on power over an OE 163 (or 198) intake. (read
this thread for more info)
If the intake you decide to run has a center divider (assuming a dual plane intake of course), the 3310 will be the better choice. If your intake does not have a center divider, the 3418 will be the better choice, but it will need to be re-jetted. (read
my dyno results from testing a 3910 against a 3418 on my own 496)
Please note that the 3910 was used in conjunction with the center divider intact, and the 3418 was used w/o the divider, as it was originally designed by Holley/GM to be used on the open plenum L88 intake.
Eric