"302" head question

Yeah its normal... I run 302 heads on a 273 and I noticed the same issue with my heads when I got them as cores. I would take them to a machine shop first and have them do a 80-degree (I hope that's right) bowl cut along with a rough cut valve job before you port. That ways you don't cut to much.. After the machine shop does the bowl and seat work, just blend the machined edge at the bottom of the cut in the bowl to the raw casting... Clean up the short turn radius and profile the valve guide boss too (now would be a good time to make sure you don't need new valve guides, if you do make sure the machine shop installs the BEFORE you do any grinding on the short turn radius or valve guide boss)..