Any 5.0 89-93 Mustang MAF will work fine, they are all the same.
For a little extra power, here's a hint...
The OEM Ford MAFs are not calibrated to injector size. The injector sizing is done in the computer’s internal programming. Aftermarket MAF’s “lie” to the computer in an attempt to fool the computer into changing the injector pulse on timing to match the increased airflow.
The only other MAF that is a one for one swap for a 93 and earlier 5.0 Mustang is the 94-95 Mustang MAF.
94-95 Mustang GT MAF - $40-$100. It is 70 MM instead of the stock 55 MM on regular stangs built prior to 94. It uses a slip on duct on the side that goes to the throttle body and a 4 bolt flange on the other. You need a flange adapter to fit the stock slip on air ducting that goes to the air box. Wiring plugs right in with no changes. *1 *2
Once your replacement 70MM MAF is in place, disconnect the battery for about 10 minutes. When you reconnect the battery and start the engine, the computer will relearn the settings for the new MAF.
*1.) Metal flange adapter http://www.kustomz.com/cat3.html Buy the TR70 for $44.95. Or spend some time on eBay looking for one that may fit.
*2.) MAF & sensor interchange
The 94-95 Mustang 5.0 MAF & sensor is also found on:
1995-94 Mustang 3.8L F2VF-12B579-A2A,
1994-92 Crown Victoria 4.6L F2VF-12B579-A2A,
1995-94 Mustang, Mustang Cobra 5.0L F2VF-12B579-A2A,
1994-92 Town Car 4.6L F2VF-12B579-A2A,
1994-92 Grand Marquis 4.6L F2VF-12B579-A2A,
Evidently the –A1A, -A2A, AA, etc. on the end of the part number is a minor variant that did not change the operating specs. You should be able to ignore it and have everything work good.