You read timing off of the ground strap.
Here's a couple good articles:
http://www.dragstuff.com/techarticle...ead-plugs.html
http://www.dragstuff.com/techarticle...ark-plugs.html
http://www.dragstuff.com/techarticle...ark-plugs.html
Since you're on Alky, you want to pay attn to where the blue annealing line is on the plug ground strap. The closer to the end of the strap it is, the closer you are to burning stuff up. A conservative tune on a blown motor will keep it at the 90 degree bend on the strap.
On a N/A motor, you can get it closer to the tip, since combustion chamber pressures aren't nearly as high.