If the 1219(B) and the 418 I/II are the same model they certainly look nothing alike.
As part of my ongoing doc sorting efforts I found the 418 Systems Description Manual and a lot of 418 III stuff. This will help me to poke around Duane Craps emulator when I get the chance, in addition to the info he provided.
Most of the WWW says that the 1218, 1219 and 1219B are simply militarized versions of the UNIVAC 418 I or II commercial models, depending on the delivery date of the unit to the Navy.
It is a little murky where the 1219 ends and the 1219B begins vs. the 418 I and 418 II. There were a lot of other models being produced at the time. No one says the later 1219B were NOT 418 III's.
From my docs the 418 II was a "minor release" compared with the 418 I or 418 III, but I'd need to do more research. For example the Auerbach Computer Characteristics Digest (1969) lump the I and II together, with the III separated entirely.
One could infer then that the 1219 and 1219B were essentially the same, only the options were different. The 1219 came with 4K RAM as the minimum configuration but I don't think you could buy a 4K RAM 1219B. Little stuff like that. I *believe* that the original 1218 was based on the 418 II, and then from there it diverged into its own unique model.