Opinions I have, I am not so sure about expertise.  I have used the 308 case for years with good results. My last outing resulted in a 250 19X which was high score for the day.   A .333 neck would allow you to clean up any brass you chose to use and I suspect a .334 would do the same.  I and others have used the .333" for years with no problems.  A lead of .020" will allow you to use even the lightest of bullet weights and a lead of .085" works for most everything up to 168gr and as light as 125gr.  A steeper angle into the rifling seems to make the throat last longer and loads using theVV N140 powder produce excellent results.  If you are considering this route I can mail or fax you a copy of the reamers I have used.  They are based on the Obermeyer chamber.....Larry Cribbs