Sorry just saw this. I honestly think your best bet is going the route I did and get Motorcraft shocks for the T-Bird. I can't confirm this yet but I'd be surprised if it isn't the same shock Ford used on the 3U2Z replacement shock kit they last made for the Mark.
Motorcraft part number is ASHV1014 they were about $25 each from Rock.
Let me know if you have any questions or need any pictures or measurements from the Motorcraft shocks. I did a decent amount of research here so I'm happy to share what I found.