With iron heads, I found that my car could take 13* on 87. I know some can't even run 8* on 87. It really depends on application. There is no linear relationship between base timing and octane ratings. I'd knock it back to 10*, and if it doesn't ping, sneak up on it 1* at a time until it does detonate. When you find where it does start to detonate (audibly), knock 2* out of it, and leave it alone.
For example, if you start to hear detonation at 14*, knock the timing back to 12*.
don't mean to hijack but i bought that 180 tstat you read about joe just so i could advance my timing. i have a problem tho, i can't see the number on the balancer, what do i do about that little problem??
Get under your car and use white out on the marks. Now you will be able to see them. Also your question 1994Vib.RedGT vary's on cars. Just try different things and you will find out whats the best to run. Also why are you running a 180 T stat?