in the old benoni the best apporach is d5 and not dxc5 so just decline the old benoni
and if they decline the Old Benoni you go for b5 . I've won lots of games with that!
Old Benoni isn't a gambit but okay... also are you talking about the Benko or the normal plan in that variation?
I'm not talking about the Benko but the normal plan in the Old Benoni after d5 by white!
This is also what can happen if white avoids the landmines!