Move the distributor gear one tooth clockwise and you'll be able to get enough timing advance to keep it running. The 348/409 engines are torque monsters- - - -don't over-rev them or they start swallowing valves. Instead of using the governor, install a good quality, accurate electronic tachometer and keep the RPM under 5500. Drag racers in the early 1960's revved the 409 to almost 7,000 RPM, but they turned a lot of those engines into boat anchors, too. The truck engines don't have the same cam and valve springs as the hotrod car engines, so the redline RPM needs to be a lot lower.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!