I am rebuilding my orginal 350 4 barrel that was rated at 300 gross hp. I am boring it out 30 over, and installing a mild cam(10% or less power). I want to have 350 gross HP(to be nice to my trans). Is it worth buying an aftermarket intake? if so what do you recommend and what kind of power gains? That would work well with a mild cam (so i can make suggestions to my engine rebuilder)

It will have K&N intake, stock manifold, with dual eshaust.

BTW 350 grossHP is equal to about how much wheel HP?

ZZ4 intake. You can pick them up on ebay for $100 or so.

350 gross HP (60s "rating" system) is probably around 275-280 net (modern system), around 220-225 to the wheels.

Look for a cam with 210° of intake duration at .050", and about 10° more exhaust duration than that; about .450"/.460" lift; and no more than 265° "advertised" duration. Stay away (far away) from anything hyped as a "muscle car replica" cam; especially the 151 cam (the so-called "375HP 327") one. It's terrible, especially in an auto car, and most especially if it's a heavy car with not much gear.

comp 268 (.454/.454) is a very decent mild cam