Can  evens  be substitute for  surely  ?  It seems to be used that way in this film called Peaky Blinders.  This Irish mobster interrogates his ranks trying to flush out the one traitor.  He says:
I've done the odds on all of you. Â Evens it's him. There's another possibility. But evens it's him.
Now this man is into horse racing,  so his uses of  odds  and  evens  appear to be fitting of the mindset-  probably jargon words in gambling (which I am happy to know nothing about.)
On the other hand,  because I am stranger to gambling,  that  usage of  evens  sounds to me like it could well be equivalent to something like  surely. Â
What's the odd of that ? -that evens is  here not as gambling jargon, but only some dialect form of emphatic words like  surely, or of the more common  even.  An even chance either way?
Or can evens be itself a standard usage, not even dialect, nor jargon? Â
And can  you even substitute  in the plain  even  for   evens.   But with that, can the resultant statement  even be a grammatically appropriate use of  even?
If you are a teenager reading this, I can see you're doing  Wha?  I can't even!
In my mind and this case, probably would be a better substitute for evens than surely would be.
The term "evens" does come from gambling and is short for "even odds" which implies a 50% chance of success. At least in the context cited. But when gamblers use that term, they're usually more certain than 50% ... so it's kind of a reverse hyperbole.
So EmmettRedd's suggestion of "probably" for a substitute works fine. So would "likely" or "almost certainly."