It seems that Mustang pans are pretty much universal for 65-70. One difference that you will find though is that they use a separate section for the seat riser. If just using pieces, it should be no big deal, but if using an entire side, you may need to do some additional fab work. On a positive note ... that would get you away from the need to track down rare Mav-only seat tracks. Repop floor pan sections can be had fairly inexpensively from many Mustang parts houses .... CJs Pony Parts is where I have gotten a lot of stuff. The ridges, etc. in the Mustang pans will not duplicate the Mav floor, but with carpet over it, no one will really care.
Fordcustom, are you going to use the Mustang seat risers? I used the 65-70 short pans from National Parts Depot, to keep the Maverick seat mounts and under floor brackets intact.
I am mounting seats out of and audi and didn't have maverick sliders anyways. I had a little rust but the main purpose of the floor pan swap was for me to lower and move my seat back (I'm 6'3")
i also got mine from ther only mine was $142 and i got mine in 5 days here is the link where i just put floor pans in my car i still like making bracets for the passenger side of the car but good luck http://mmb.maverick.to/showthread.php?t=85107&highlight=floor+pan+reso