During flight, electrical fumes, smoke, and sparks began emitting from the circuit breaker panel immediately left of the pilot's seat. The pilot was forced to move to the right seat. He tried to suppress the sparks with a chemical fire extinguisher and tried to isolate the source of the electrical fire, but was unable. He declared an emergency and landed at Savannah, GA. An investigation revealed that fire had destroyed much of the wiring behind the circuit breaker panel and several holes were burned through the fuselage skin. Both over-voltage regulators were burned out and all radios and voltage regulators were destroyed. The battery had over-heated and spewed smoke and fluid from the battery compartment. The circuit breaker panel had been reinstalled without a phenolic spacer on the forward side and was bent inward in that area. This spacer was needed to assure space behind the panel. The foam material (lining for additional insulation) had become brittle. A compass system and DME had been installed on 11/16/81.