for a 306 i'd go 165, the runner volume is better suited to a 306 and they flow EXCELLENT for the runner size.
the 185s move more air but the increased runner size will require the 302 to turn some higher RPM to move enough air to actually use those heads.
not to mention if your running stock pistons the 185s probably wont work. the 185s are an inline valve heads and are 2.02/1.6 and you will probably run into PTV contact at the edge of the eye brow notches on the stock pistons.
the 165s only have 1.9/1.6 and shouldnt run into any PTV problems, but its still good practice to check regardless of what you run.
i think the 165s will work better for a N/A 306. not saying the 185s wont work well the 165s.
now on the other hand if your going to run forced induction you could use a bigger runner head like the 185 if you like.
but the 185s for a N/A deal would work better on a 347 or 351 etc.. something with more displacment that is going to move more air at lower engine speeds.
The 185s would fit those parts better. Be sure to get the appropriate springs to match that cam. Check the lower intake, make sure things line up well with the heads as well.
No the results wont be the same. While its still in the small block family the 347 is built more for heads like the 185's while the 302 is better suited for 165's. Look at the HP differences in that link w/ the 165 VS 185 on the 347, you can see that it needed the 185's to fully breath more. Your 306 is much much closer to a 302 then the 347. It all depends on your combo now though. If you have a good flowing intake and a good cam you can pull off the 185's on the 306