Since the usual "upgrade" involves a V8 engine an an automatic transmission, I think a self-contained assembly that eliminates the bow-shaped original linkage and incorporates a spring-loaded plunger that just bolts to the floor in the general area of the stomp pedal would get the job done. IIRC, isn't there supposed to be a bellows-shaped rubber boot around the stomper pedal? That could be used to conceal the mounting system for the fake pedal. The push button switch could be mounted on the firewall side and the original hole in the firewall could be used for the pedal shaft to push through to it.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
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