"-" replacement

It IS possible. As I said use URL replacements:
-=>whatever_you_want

It is working, if not - you are doing something wrong.

right... I did something wrong  : I tried again and yes, it works now  ;D
thanks

I recommend you don't use underscore to separate words since google will consider only one word.

For example:
red-car (2 words)
red~car (2 words)
red_car (only one word)

On the other hand "co-existance" is one word. So the URL replacement "co_existance" seems appropriate in this case.

I recommend you don't use underscore to separate words since google will consider only one word.

the problem is that I am too good  ;D I use "-" for years directly hardcoded in my titles.
btw, this "-" instead of "_" is overrated.

On the other hand "co-existance" is one word. So the URL replacement "co_existance" seems appropriate in this case.

In this specific case yes, for sure 

I think that there's a problem with the replacement, the old urls are indexed with '%11', google will find new urls with '_' but the old urls with '%11' are not 301 redirected to the new with '_', so this could be considered duplicate content.

How we can add the 301 redirect?