<VV> drain plug question

[Randy (Cap'n) Hook]

I'm working on a '65 500 coupe.  I'm installing a 4spd where the 3speed was.  But I noticed that the '65 diff just has a boss cast in the case (no drain plug), whereas the '61 diff has a drain plug drilled and tapped and installed.  Since I have everything apart at this juncture, is the '65 diff case made the same as the '61 case?  If so, that means I can go ahead and drill and tap it and install a drain plug in it,  with no issues, right?  
Inquiring minds want to know.

Thanks.  Randy (Cap'n) Hook
Hopewell, Pa
'65 500 coupe, 110/4spd