Here's another article from Henry - this one is about how to tune a Roush 427:
http://www.automotiveu.com/tuningperformance.htm
Using the Barry Grant initial timing guide we decided that 18 degrees of initial timing would work quite well with the camshaft that is in this engine. We then recurved the distributor so it would give us 16 degrees of mechanical advance that starts advancing at 800 rpm and is all in by 3000 rpm to give us 34 degrees of total mechanical advance. The MSD distributor that is in this engine did not come equipped with a vacuum advance and since the reason the customer selected this engine package is maximum power the vacuum advance was determined to not be a priority. We then reinstalled the recurved distributor into the engine, set the initial timing at 18 degrees BTDC and confirmed the total advance to be 34 degrees BTDC. The tech literature that came with the engine specified the total timing was not to exceed 35 BTDC.