charles is Right...but if you have no access to dyno...test and tune the car...normally Higher Timing is gonna be more bottom end and less top end...same with valve lash...a tight lash will have more bottom end, looser lash top end.
in the past i would just keep inching it up until the 60 ft slowed down noticably or..keep in mind don't be fooled by Tire spin..you should be able to feel the diffference in the seat your seat....you can always feel that certain vibration when she is running crisp...
I personally would start out with 36 and work up toward the 40 mark and see how it feels
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Bjuice..
"I'M YOUR HUCKLEBERRY ! "