340 idle problems

I need to find a shop that can do my disty work near Minneapolis. I don't
want to give up my points disty with pertronix ignitor, but when I get my
car running great it's at about 17 before, that puts my total at about 42 which
as I found out makes me go ping, knock, ping. Not so good for motor life. If
anyone has a link on how to limit the advance I'd much appreciate it.