Many years ago, the 428 had 8.9 compression, magnum 292H hyd-flat cam and 225 cfm ported heads. So, like you, a cam too big for the compression, yet it ran a best of 12.31 in the GTO.
With your Rhodes lifters you will be fine for street driving with the lower compression. Like what was asked before, do you' need' the extra power? I think if you do the work of milling the heads and 1.65 rockers, then check for rocker stud length and pushrod length, you may have to purchase both, plus new springs. I feel it is not worth doing all that with stock heads. If you need the extra power, also port the heads.
As for the clearance in the heads for 1.65 rockers, you may need to remove material the whole length of the guide hole, not just the top portion.
Actually, when I sell the GTO I will put those lower comp heads back on with the RA4 cam, Rhodes lifters and 1.5 rockers. I think it run good enough for the next person.
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