no chance you gonna get 270 + with a cam that small
to give you an idea, some of our locals have just installed
224/228 112lsa - 270rwkw - (hsv headers, zorst, otr, m6, valve springs)
222/220 - 238 rwkw - (try y's, twin 3", monaro intake)
OTR, try-y's, 1.8:1's, twin 2.5", mafless tune, auto...