I think the orginal posters question was very well answered in regards to the timing light question.
The discussion has turned to timing and heres some reading from our
www.gasolinealleyshops.org site in regards to our dyno testing results.
You can wander around the site or read one dyno day here
http://www.lindertech.com/gas/8-21-07.htm
We still run this truck , nowdays at the ECTA event in Willimington Ohio and hopefully this year we will get our big stroker ( 304 ci) motor in the truck and go after the new record ( 110 mph). Bonneiville has gotten too expensive to travel fuel, room board etc so we love the 150 mile ride to Willmington.
All in all we have approx 5 days on the dyno and have found that anything over 28 degrees drops of the hp quite a bit...
Enjoy........