67conv6cyl... did you read this? Is your car LOS or NOR build?
(As an aside: I did not take notice of this initially, however through out my 48 month non scientific study and recollection (worth what it will purchase) recalls LOS cars having indented head bolts in positions 2 & 3 where as the NOR cars had RBW's like pictured. )
The RBW's for the NOR built cars seem to be available.