That block casting number is unique to the '68RA 4 bolt, '69 RAIV 4 bolt. Besides the four bolt mains that were drilled and tapped and matched with caps, I'm not sure if there were any other differences in the castings. Certainly there were no differences in the external dimensions, as you can bolt all the RAIV parts on a non-RA block, and can tap and align bore for 4 bolt mains on many non-4 bolt blocks. There was also a 4 bolt main 1969 9792968 RAV block.

I don't believe there were any casting differences between the HO/RAIII blocks and the standard and low performance engines. My '69 YT 400 is only a couple of part numbers different from a '69 RAIII. However, there are others on this forum who have a lot more knowledge of these engines, so I defer to their experience.

I forgot to mention that for '69, all 400 except RAIV used crank 9795480, and RAIV used 9795481. Both are listed as Nodular Cast Iron cranks, and the RAIV should be marked Armasteel along with the part number. This chart indicates that all dimensions were identical, but the RAIV calls for .001" more clearance.
http://fiedlerh.home.att.net/PontiacCranks.htm