The Dyna III was an earlier version than the Dyna S pictured. The Dyna III had a remote mounted box, like the Gerex, and had a good reputation for reliability. I believe that it still used the stock advance mechanism, like the Dyna S. I believe only the Dyna 2000 used electronic advance?
As far as drag racing, since the stock advance is all-in at about 2500 RPM, I don't see how locking the advance would help.