Jon,
Factory specs for the Berkeley 460 Pack-A-Jet timing are 10' BTDC at 850 rpm idle and 40' total advance. I recently suspected false timing readings on my stock 460 and noticed that the harmonic balancer had slipped by about 18 degrees! Thus, an indicated 10' advance at idle was actually 28 degrees. Makes starting the engine a bit tough! Check the orientation of the timing marks relative to the keyway on your balancer against those of a brand new one. The rubber press fitting holding the inner and outer halves together can deteriorate, causing the slippage and could be disasterous if the two came apart at high rpm. Good luck.