Look under the manifold toward the rear of the engine for the temp sender. Base timing is around 6-8. Factory specs are just a guideline on any vehicle this old simce gasoline formulation is nothing like it was then. My 72 300-6 is real finnicky about the timing. Factory spec is 8 but it pings on 8. Set it back to 4 and it has a noticable loss of power. It has to be 6 degrees advance with very little tolerance.