This MAF is reportedly from a Mark VIII (I can measure it if you like)that has been polished, but the electronics is from a '91 5.0 (also from an SHO and other models). This will require someone to acquire and mess with the MAF's transfer function and adapt it to their tune.
The way that I would identify that MAF is by using Clint's EA software.
I would install it. Download some transfer function to your tuner, it
doesn't really matter. Datalog the car as long as you can stand it.
Pull the log in and let EA correct the MAF. Rinse and Repeat. In less
than 10 runs, you should be able to flip through the existing MAF
transfer curves in EA and find a match. Then use a transfer gauge to
get an accurate inside measurement. Then you can sell it with
confidence as a XXmm MAF with a Xxxx transfer curve. If you don't have
the Engine Analyzer software, the process just takes longer. It can be
done in an afternoon.