The Allison ECU voltage alarm points are programmed for 35V hi and 10V med-lo, 8V low, 7V ECU shutdown, but there is a note in the Allison troubleshooting manual talking about a specific 24V VIM this makes sense as the relay coils(like for the exhaust brake) are powered by switched input voltage so they have 24V relays in them. I think it may also have a 12V relay in it for neutral lockout, there is a 12V relay listed in the 24P manual as a part in the 24V VIM.
A little research and I found a different P/N for the two VIM’s
For WTEC II, the 24V LMTV VIM is P/N 29509889 (parts descriptions also call this a regulator)
The 12V VIM P/N is 29509886.
if you google these P/N’s you will find pics showing they have labels for 12V and 24V...