If a true 10.9 or thereabouts lol, what do you expect to gain by advancing it?
You should have lots of cylinder pressure already, so it can't be that......
The Wallace points to 160 psi. With iron open-chamber heads that's about the limit for pumpgas.
advancing to 104 is pointing to 169 psi. almost a sure recipe for detonation on pumpgas.
I'm with @RustyRatRod ; highly recommend a compression test.