I found an ebay auction for 6 Military Senior oil filters.
Here is what they look like:
The appear to be Military Senior filters, but there are several odd bits:
They are Gray
The lid is 'domed' much more predominately than the AC filters from the factory.
The decal is not applied.
It comes with a filter element.
The intake and outlet boss in in line with each other (from what i can find only the original AC filter bodies had the offset intake/outlet boss)
Popping the NSN into any of the numerous look up databases is shows that the part is specified as a component by: (that's if I read the codes right)
64829 - Arvinmeritor Inc 2 11.11 %
That name is associated with the M-series 2.5 ton trucks.. so most likely these parts are for an M211 or M135 gasoline engine.
I do believe that they would bolt right up to a GMC 270, but would not be a factory item. I think the domed top would also be highly noticeable to the trained eye.