Like RolandT3Speed said, this is one of the #1 killers, my suggestion would be to contact Classic Creations of Central Florida to see if they could do a complete cowl replacement as they did in this Mustang Monthly article. Not only do you get a complete new cowl, but the reproduction parts are edp coatedwhich will help prevent this from happening again. As soon as dynacorn has a complete cowl assembly for the 65/66, I will be doing the same.

http://www.mustangmonthly.com/howto/...ent/index.html

 

Yep, I replaced the upper and lower parts of the cowl and it wasn't that bad. Not after replacing frame rails. But if your car is a completecar, it will need a lot of dissasembly to do the job right. No telling what kind of issue you have without tearing it apart to see. If it has never been replaced it is probably not good. The water can get down inside your car rusting out the lower cowl, cowl sides, floor, etc.and ruining carpet doing a lot of damage. Consider replacing/fixing the cowl a major job.

 

I just took off the front bumper, hood and fenders, then cut the sides off the cowl. Then ireplaced the gasket things (what the heater is attached to, alsowhere its leaking from) and sealed it up with some silicon. Then for a little extra insuranse from this happening agian, i painted the inside of the cowl (a little tricky) andfloor panswith POR 15 rust remover/stopper. So far it has worked fine and only costed me around $75 and about 6 hours of work. Its a less expensive and less time consuming alternative.

 

One more site for cowel repair, it's at the bottom of the 1st page.

http://spectrum-photo.com/mine/progress.htm

And yes, it is THE killer. Whatever you do, however you do it, fix and don't ignore it. Even the cover won't stop the rust from continuing to kill your ride.