Codification?
You need to use a thrust bearing that fits the block, if the thrust is small...then the machined seat it sits in won't accommodate the '74 'larger diameter' thrust bearing.It just wont fit and seat.
With the exception of the thrust bearing either set fits either new or late block. So heres the other end .. it doesn't matter that the crank thrust surface is larger or smaller diameter/face than the bearing.
