How do u get into the cowl on a 66 stang?

Put a cat in!
Try blowing some air in there. High pressure of course. You may need to get to the drain area on one side and help the stuff come out.
That's all I can figure.

You may need a wand type air hose attachmnet.

think of it as an air freshener, LOL

i wanna know how the mouse got in there

Those little buggers can get into just about anything. Give them a hole about the size of a dime or nickel and they can some how squeeze in. I hate 'em almost as much as I hate squirels - don't ask.

They could easily get in thru the fresh air vent or heater box.

Can you spell Car Wash !!!!