I'm doing mild ls, build p30's, arp rob bolts/headbolts, p&p and im going to put it on the bottle.

I want to go 404 because i know i they have more potential, but do i need them? I know a guy who has a set of 403's for sale for a good price, but if there going to hold me back in the long run i dont want to buy them.

So, 403 or 404's.

if its a street car...just get the 403's

Yeah get the 403s if you are going street, 404s for the track. The idle is very rough on the 404 unless you plan on driving at 7000 rpm all the time.

if u have upgraded pistons and bumped up your compression 404 are fine u can solve the idle problem by tuneing it but the idle is not to bad with the 404 if u plan on going bottle i would keep the low compression and keep the bull sht l/s pistons just make sure ther in good shape for extra insurence i would upgrade the valvetrain for the ha ha juice

i agree with bakki 404 cams are nice. some people get mixed reviews because they may not idle right because of many reasons.
i had 404s and they didnt idle at first because of wrong valve adjustment after that it fixed a lot but got better after tuning you cant even tell now. these are with p30 pistons too. i wouldnt run to big of a shot if your using oem pistons maybe around a 50 to 75 tuned. plus what tranny are you using for this set up.

Yea the main reason they are not "streetable" is because of the rough idle, if you can deal with that they are fine.