I'm pretty sure they don't sell that rubber by itself. You might have to buy the entire cowl. A few years ago I was looking to replace mine but didn't want to spend $200.
Well poop. It's one piece with the cowl grill and you can't buy it seperately. My friend just replaced his whole cowl grill because it cracked. Unfortunately we have already tossed the old one. I didn't even think to pull out the old rubber pieces in case someone needed one.
Thought I'd update this... I found the left hand rubber hood hinge seal, thought it might work on the rh side.. wrong ... Ended up buying the cowl with the seals already attached very confused on why you can buy one side and not the other?? Anyway I am tired of messing with it and looking at it, bought the entire cowl.
94-98 MUSTANG COWL VENT COVER
Your Item No.: F5ZZ-6302228-BA
The rubber pieces go on pretty sweet though if you could find them..
Remove the weather seal under the hood, then the 3 screws.... snap the cowl out carefully.