I believe the foxbody Mustangs have the same or similar boot.  If I remember tonight, I will pull the hinges off my 90 Mustang parts car and check.

What is the point of those boots anyhow? Every car I have has holes in them & it's not like the cowl doesn't get water in it already. At best they force water to the vents that may pour out the hinge hole or prevent excessively rusted hinges. I really have pondered this.

I thought I read that those fox Mustang boots would work but could not find the link.  Maybe drill the fox Mustang boot rubber to match the Pinto bolt pattern.

Pinto5.0, those hinge boots along with the seal strip at the top of the firewall have a couple functions as I see it: 

At speed, there is a high pressure area formed at the base of the windshield.  This high pressure helps force fresh air through the vents.  With out the boots and seal strip, some of this high pressure air will flow into the engine compartment putting back pressure on the radiator reducing air flow through it (loss cooling) and also reduce the amount of fresh air flow to the driver.

At low speed or at a stop light, these seals keep engine odors/fumes from entering the fresh air vents.