I run the RHS heads on my 360 magnum, well worth the 875.00 i spent, i'm sure in stock form, they will be like a race head on your 318, stock they will support 450 HP, ported with larger valves there good for around 550 HP.
That would be with a Stroker, a Roller Cam and 12:1 Compression. You could possibly see a REAL NO BULL 550hp with those heads. This is from experience building one using Ported INDY/RHS LA version.
