set it to the stock 6 degrees BTDC, then advance it by ear till it starts to pink, then back it off a tad. Take it for a test drive and keep an ear open for pinking, if you get any, back the timing off a bit more.
If you want to get the very best out of it, make sure you run it on optimax for a couple of weeks, make sure you get rid of any cheaper stuff. The higher the octane the more advance you'll get out of it!