Musclebeech, you got those two brown back cards from me. They also come with black backs.
The 1976 Hostess set has some interesting variations (not including the Twinkies cards). I only collect Orioles, so I'll address the 8 Orioles from the set. Depending on which product the cards appeared, there were not only black and brown backs, but also cropping variations of the cards themselves. If you aren't confused yet.. Here we go.
This is what I have for 1976 Hostess Orioles cards
#13 Bob Grich (Back printed in black only)
#36 Brooks Robinson (Back printed in black only, 2 photo cropping variations on front)
#36 Brooks Robinson (Hostess proof card - Back printed in brown)
#56 Jim Palmer (Back printed in black only, 2 photo cropping variations on front)
#76 Ken Singleton (Back printed in both black and brown)
#98 Lee May (Back printed in both black and brown)
#118 Don Baylor (Back printed in both black and brown, 2 photo cropping variations on front)
#121 Mike Cuellar (Back printed in both black and brown, 2 photo cropping variations on front)
#139 Mike Torrez (Back printed in both black and brown, 2 photo cropping variations on front)
The cards with brown backs appear to have been distributed on less popular products, making them a little harder to find in my experience.
The same thing happened with Post Cereal cards from 1961-1963. Almost all cards have cropping variations depending on the product they appeared.
Hope this helps a little.