I purchased the replacement seat pans for my 67 cougar and they came in as mustang. these are slightly different. the biggest difference is the height of the pans. they seem to be about a 1/2" higher. Anyone run into this before? 
Yes, Mustang had less foam thus higher profile to compensate. They will work and some people who are short prefer them. Used is all you will find if you want Cougar correct. Let me guess, the Mustang place you bought them from said Mustang and Cougar are the same?
Good time to cut your seat pan down if you are tall as well.
We prefer the term ‘vertically challenged’ 
Don, your right ! In fact they where adv as cougar only if I recall correctly. Cutting these down doesnt seem like a good option due to the flange and the underside stiffeners. way too much hassle. since my car came with no seats, i guess i can just acquire mustang seats and the issue goes away? Thanks for all your help folks.
Cutting the floors & toe boards out this weekend and hoping ot get the new toe boards welded in.
If you are using the floor to firewall patches from ‘that Mustang place’, I would like to know what your experience is.
My body guy rejected them for fitment problems, I do not know what went on between him and this drivers patch, but the patch lost.
If you only need the lower part of the patch, it may actually fit there, but near the top there were lots of gaps.
Went with a complete firewall from WCCC! That will match my complete lower cowl and complete floorpan (sheesh, what have I done).
In for a penny, in for a pound I say!
Cutting the seat pan does take a little time, considering the bracing. I think I did it it in a day,counting cutting it out of the car. But we’ll worth it if you are 6ft tall or so.
I just want to say that I agree.
DEVILDOG, i had no problems with the mustang toe boards or the full floor boards. im sure the toeboards did no encroach that far up the firewall. i only cut to where it was thick enough to weld to which was a couple inches below the steering column hole. your photos are very scary. not that its any of my business but looks like someone let the cutting tool run away on your firewall. 
I do know i got quotes of $3k + parts to do my floors. Labor is what kills you on hte projects. I borrowed a welder, bought parts and spent about 80 hours on the install and am extremely happy with the results.