Thanks Dog, backup is always appreciated. When the "thin wall" casting started in I think the '75 model year the first # went from a 3 to a 4 in the block casting # on the side of the block on both sb's and bb's but how/why alot of these "later" ones ended up being thicker I dont have a clue.

live every 24 hour block of time like it's your last day on earth