Check out this boxscore from the 1984 Caeser's Palace Grand Prix. It lists AJ Foyt's engine as a "Gilbrt" (the engine names are abbreviated, i.e., "Coswth", so I assume the full name was "Gilbert"?).
I am a pretty avid Foyt fan, and was following Indy car racing pretty closely long before and after 1984, yet I don't recall ever hearing of such an animal.
This wasn't the old Chevy V-6 hand-grenade, was it? Any info out there on what this "Gilbert" might have been???