According to NPD catalog, there is a difference between 69-70 mach1 and 70 standard high back foam. It was listed as "Economy seat foam" though.
Also, in the NPD catalog, The professional quality/precision molded foam from ACI says 69-70 mach1. There was no listing for 70 standard high back. I couldn't see where seat foam would make a huge difference between 69-70 mach1 and 70 standard high back. Save for the seat latch cutouts between 69-70. JMO