273 engine identification.

R dont know
273 Cubic inches
8-5. My guess is Aug of 1965 assembly date

My feb of 67 built dart has an engine assembly C273 12-6 (december 1966)
By all accounts the C of C273 = model year 1967 273

There is also a small B which might mean 0.010 undersized main and crank jurnals

and an upside down 319 stamped into the area as well, unknown meaning, posabily from a rebuild?

Look towards end of post
How to ID a Small Block Engine Block: