ABOUT 9 MIN AFTER TAKEOFF, AS THE PLTS WERE MNVRG ON A LOCAL TRAINING FLT, THE ENG LOST POWER. AN EMERG LNDG WAS MADE IN THE ONLY AVAILABLE PLACE, A CLEAR CUT AREA OF AN EVERGREEN FOREST. DURING THE LNDG, THE ACFT COLLIDED WITH ROUGH TERRAIN & A STUMP. FUNCTIONAL TESTS REVEALED THAT BOTH MAGNETOS WOULD PRODUCE A SPARK AT AMBIENT TEMP, BUT THEY WOULD NOT OPERATE WHEN HEATED TO NORMAL OPERATING TEMP. BEFORE THIS FLT, THE 1957 MODEL ACFT HAD BEEN IN STORAGE FOR AN EXTDD PERIOD OF TIME. RECORDS SHOWED THAT AN ANNUAL INSPN HAD BEEN PERFORMED ON 4/3/87 AT 1294.3 HRS OF SVC. THE NEXT ANNUAL INSPN WAS JUST BEFORE THE ACDNT FLT AT 1294.8 HRS. THE COILS IN THE BENDIX S4LN-20 SERIES MAGNETOS INSTALLED IN THE ACFT WERE REQUIRED TO BE REPLACED BEFORE 2000 HRS TIME-IN-SVC IAW AD 73-07-04 (ISSUED IN 1973) & BENDIX SVC BUL #560A. THE AD HAD NOT BEEN COMPLIED WITH. NEITHER THE AD NOR THE SVC BUL SPECIFIED A CALENDAR TIME LIMIT FOR MANDATORY REPLACEMENT OF THE MAGNETO COILS.