hey do we go by OEM settings or does it change with the new Dizzy! Mine is set at 20 BTDC and seems to run good?

Also notice that the boys 73 with a electronic style dizzy is set at the same?

Sorry mine is a modified 260 engine in a 77 with trip webers!

One answer would be to time it at 3000 rpm. Should be in the mid 30's degrees at that engine speed. Then whatever it is at idle, it is. I think you might be able to adjust the mechanical advance on that distributor. If you can then knock it back to about 15 degrees total advance, then you'll have your 20 degrees at idle and you'll be in the mid 30s total. You'll need a timing light with an advance knob to time it at higher rpms, unless you have a fully degreed harmonic balancer.