I am having trouble determining whether #456 or #733 11" flywheels are correct for what applications.I have several of these flywheels both nodular and not.Is there any rhyme or reason to this?I'm assuming the letter N after the casting # means Nodular,additionally I have some where the word Nodular is there and complete and if I remember correctly I had taken those off 1970's truck applications.Specifically what would be correct for a 67' L-78 Chevelle?Please help.Dennis