This would depend on a few things.
First, the condition and tune of your engine.
The altitude where you live/mainly drive.
And how much you want to pay for higher octane fuel.
Put the highest octane you want to run and crank the timing past 12 deg.
figure it out for yourself. It varies by engine. I am running 7*, but I am nowhere near stock and the computer I am using adds a bunch of timing compared to stock.
10* is base timing. But some people like to run it all the way up to 16* advanced. It just depends on the motor. But you don't want to advance it too far, or else you will get detonation and loss of power. Be very careful not to detonate it.
1986, is that a carbed engine? I thought in 86 EFI was optional, with the rest being carbed. If it is carbed, then I'm not exactly sure.
If you have a Haynes or a Chiltons manual then it will tell you what base timing on your car is. Then fiddle around with it from there.