Replace an header authorization request with policy or iRule doesn't work ...

Try below. Modify the names of the header if needed. You can enable logging to see if it's replacing as expected.

when HTTP_REQUEST {
if { [HTTP::header exists "X-epsilon-Authorization"] } {
set value [HTTP::header value X-epsilon-Authorization]
HTTP::header remove X-epsilon-Authorization
HTTP::header insert Authorization $value
} else {
 return
 }
 foreach aHeader [HTTP::header names] {
  # log local0. "$aHeader: [HTTP::header value $aHeader]"
      }
}