If you have the later type bearing inserts, I'd agree it argues yours may be more like the 56...but in all honesty the topic of the neoprene seal is not treated on the GM Heritage Pages and reading Chevy shop manuals (all the ones I have) there's no mention in them, either. If anyone has something official, I'd appreciate seeing it. Every single thing I've heard about this seal (for over 50 years) is 100% heresay from mechanics, dealership parts people, folks on internet forums, etc. I have some very good info from GM dated 1957. Not a single word about this type of seal is in there.
