Have them slowly depress the pedal while you watch the linkage at the carb. See how much the pedal goes down before the linkage moves at the carb.
For '67, the pedal pivot arm bolts to the flat metal linkage that is behind the engine (they used a cable from '68 on). There is a keyed slot in the flat linkage. I found that after 40+ years that slot had been wallowed out and I had several inches of pedal movement before the carb linkage moved.
They make a nice reproduction of that flat linkage behind the engine that will remove that play. It is a royal PITA to get to with the engine installed though. I had to purchase a ratcheting 1/2 inch wrench (ratcheting head) with a locking swivel head from Sears to get to the bolt that holds the two linkages together.
What a difference to finally have all 490 horses at my disposal.
Another issue could be the metal bracket the pedal arm passes through at the firewall could be loose.
2012 Mustang Boss 302 #1918, Competition Orange. FGF replacement 2006 Mustang V6 Pony, Vista Blue. Factory ordered. 2019 BMW X3 (Titled to the wife, but I'm always driving it for her. So I'm claiming it) Old projects, gone but not forgotten: 1967 FB 400, original CA car. After 22 years of work, trashed by the guy who was supposed to paint it. I had to sell it. 1980 Turbo Trans Am 1970 Mustang fastback, 351C 4Bbl, auto 1988 Mustang GT, 5 speed 1983 F-150 4x4, built 302 1994 Chevy K2500 HD 4x4, 454 TBI
