I don't no what your budget is,If you bore it out your looking at new pistons plus cost to press them off and new ones on and then balance everything.keep in mind it depends on how thick your water jackets are,that will determan how far you can bore it.(IE)bore it to much thinning water jakets will run hot on street.If Tango means 60 over to get the same bore as the 327 your jackets on your 307 might not work,I don't no for sure on A 307 maybe TANGO can answer that.I no some blocks have thicker castings than others.I like 307's if your just going with A rering kit and some bearings stock with A good hone job ok,I have to agree with EIRK on this one.correct me if im wrong but can't you put a good set of 350 heads on a 307?.