Dave
the standard difference between go and no-go is .005. I won't tell you that the headspace will be okay (one slip) .. though I rechambered by nef 45/70 to 120 with little problem.. make it TIGHT as possible .. IN other words, if you are comfortable, then do not ADD anything .. remember, your reamer has at least .005 more "neck" than the drawings, to allow for case stretching.
my norma brass was a hair smaller than that .. which is why i am so focused on being CAREFUL with setting the headspace right ..