to answer some of your Questions,
the Wall Jack is a standard RJ11-W with the mounting lugs on the top and bottom,
the opening of the sign has about 1/4 inch on either side
there are a couple issues, from the top of the opening in the sign, it is 1 1/2 inches to the bottom of the braile lettering they are having on the sign,
we had been using the standard 2554 wall phone however the height of the top of the 2554 covers the bottom 2 lines of braille lettering, from a realistic standpoint of someone reading the Braille you need 1 inch from the last line to the top of the phone,
the Cortelco 2354 would work however they quit making those several years ago and there isnt a direct replacement for it (at least not that I have found) I have been using some cortelco 6150, however that requires modifing the sign (taking a 1 inch piece out of the bottom of the opening to slide it up
as to what I am looking for in a replacement is
1. something that is durable,
2. will be ADA friendly aka stick out no more then 4 inches, which the viking ones did,
3. has a dial pad allowing the user to dial numbers listed on the sign,
I have looked at asimitel, I am moving away from the armoured handset cords as it is More of a Pain then what it is worth, (as I get frequent complaints about not being heard I have looked at scitec and teledex, however using either of them would require Re-engineering the sign because of the Braille