1,72 rockers with stock head and cam?

Thank you! I save the money... Another thing! How much can I mill my stock heads and how much is it worth in torque/hp. We have 95-98 octane petrol in sweden.
I want to go 13,5 with stock heads, Cam and intake........

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-87 GT, K&N, 5-speed, Walker exhaust, no air silencer. timing
75000miles. This vinter 3,55 and mac 15/8 and H-pipes
14,61 and 95,59mph