The chart for 1985 says EXC. 4-64Z-R10 and the any other is 10-12.5.
I think you missed the EXC.
So yours is base timing (no advance) + 10-12.5 = your advance.
Just run the distributor scope at 1250 while you bend the tabs until you get a 10-12.5 advance on the spark dial.