Yeah you go with the Pypes system with Hi-flow cats, with the picture you are showing I strongly feel you will scrape. The cats have scraped a few times on me.
The closer you get your headers to fit to your floor the hotter your car will get inside..
I have a set of Kooks LT's on my stang and the floor gives off a lot of heat.
Second the heat issue. Noticed during mustang week on the strip, the floor was hot. Back seat bottom was hot as well. Whole frickin car was hot. Make it in April or October!!!!!!!!!!!!