A well cooled engine should not be cracking heads. I'm going to do 302's next summer. Have the heads boiled out and passages cleared.
In keeping with the cam question, gear ratio dependent, the 270 could be OK. I just don't know the ratio. A cam to improve your combo, but not change it's operating window, I would look at this cam. A split duration works very well with stock heads or a mild porting. Click this; http://www.compcams.com/Technical/Search/CamDetails.asp?PartNumber=20-222-3
