45 Cylinder liners

Do WLA 45 cylinder barrels have a pressed in liner, or are the barrels designed and manufactured such that the liners cannot be replaced.
If there is a separate liner, what is the part number???
What about old liners. I see there is pistons available from .000" up to .040"
If the liner is out to .040", Is that it?? Does it then become a doorstop?
Thanks Keith

[Pa]

Stock 45 cylinders are cast with no liner sleeves. HD produced pistons for the 45 Servicar up to .070" oversize. Liners are available for 45 cylinders.