Chrome 427 style,"cookie cutter" oil cap correct for GT 500 or?

[Dizzy]

What would be original application for the cookie cutter ? Thanks for any input!

[Bob Gaines]

What would be original application for the cookie cutter ? Thanks for any input!

Most prevalent that I have seen was 67 427 Fairlane with thermactor or 67 GT500 with thermactor . They were also used on any 427 smog equipped engine in full size cars of the 67 time period. At least that is the only other applications I am aware of .There may be others.  Non smog cars in that era had the taller open emission caps which vented the fumes from the open vents holes on the bottom side of the cap. The smog cookie cutter style cap on the other hand did not let any fumes escape period. The smog system recirculated the fumes instead of letting them get away into the atmosphere and fed them back into the engine to be burned.