That's not a valid Ford TSB number. But, since my curiosity was now peaked, I did some more research on this. I went back to my service guy at the Ford dealer.
Turns out when we were doing the TSB searches we were doing searches ONLY for a '95 Mustang GT, because that's what year mine is.
This time we looked for any year AODE Mustang from '94 through '98. We found it!
It's TSB 94-26-9. It's called a "Valve Body Reinforcing Kit", part number F4AZ-7F282-A. The kit includes a valve body reinforcing plate and 4 new bolts. It's a round plate, the bigger of two round plates that bolt to the valve body. It's designed to cure the valve body cross leak symptom that you mentioned.
The GOOD NEWS is that your car already has it because it's a '95! This TSB only affects AODEs on '94 Mustangs, Thunderbirds, and Crown Vics.
There is another TSB (TSB 97-16-7) that concerns the valve body cover plate, but that only affects '94 and '95 AODE Mustangs IF you are replacing the entire valve body with a new one of the '96 and up design. The '96 and up VB replacements use a thinner valve body COVER that seals better against the VB-to-Case gasket, PLUS it has 13 cover bolts instead of 6 bolts like on the old '94/'95 VB design. The VB cover is a big plate that covers and seals about half of the entire valve body.
So, the only way to get that new VB cover with the better seal is to replace your '95 VB with a new '96 and up valve body.
I do have the full text of both of these TSBs but I am not in a position to post them right now. Maybe later.
Hope that solves this mystery once and for all!