regarding the accuracy of the factory plate/cams I've found no more than an half of a distributor degree difference in actual degrees vs what's stamped. for instance a 9 degree plate may be 8.5-9 degrees. never enough to be any kind of "make it or break it". I keep it fairly simple but i'm fortunate enough to have a variety of factory parts and springs. some 5th grade math and a timing tape are your best friends.