What blocks do I have

I've built my share of small mopars and started to check my "B" blocks I hoarded for years to finally get working on my first stroker. I have 2 early 70's that both mic @ 4.320+/- which is the bore for the 440 "RB", these should be 4.340 minimum.
The markings are:
casting- #3614230-6 dc- 11/23/71 Id pad- #H400 114E pan rail- #C201766
casting- #3698630-400-5 dc- 5/15/72 Id pad- #J400 728E pan rail- #3104971
I have a 78' 440 motorhome block sitting next to the B blocks and am well aware of the differences. How could I have B blocks with a 4.320 bore?
This one has me stumped.