A custom grind is always better, however the e303 can be used with out too many supporting mods.....The b303 is a little more agressive and will respond with better heads.
I made 243 with an Explorer intake and E7 heads. Other mods were EL headers, MAC Prochamber/cat back [FONT=Verdana, Arial, Tahoma, Calibri, Geneva, sans-serif]CAI and a short belt (no a/c or smog pump)[/FONT]