The Porsche factory https://pbase.com/9146gt/image/54418483 installed the interior ignition kill switch in front of the driver, by the windshield cowling. Note that the switch is mounted under the sheetmetal https://pbase.com/9146gt/image/54417622, as opposed to having the switch assembly bolted on top as it appears was the way the part was originally designed to be installed, from the top. Having said that, I have yet to see a GT installation with the switch mounted on top. The following is an installation sample photo of the interior kill-switch in the factory built Alfa Romeo GT https://pbase.com/9146gt/image/141452171 Note the use of a 'removable key' and how the mounting bracket for the kill switch was so crudly made.

A common-thread among several Porsche factory built 914-6 GT cars, notice the use of cheesehead bolts for the kill-switch install in the cowling. This is a 1980 period photo of the Alfa GT (prior to any restoration) https://pbase.com/9146gt/image/159011674. Here is yet another sample, the Monte GT https://pbase.com/image/54417622 - Wondering about the small rubber boot protecting the switch swivel from dirt and debri? That's a simple distributor cap spark-plug wire rubber boot. Very clever!

A few more installation photos from other well known 914-6 GT cars; the Collier GT https://pbase.com/9146gt/image/89596757 the Bozzoni GT https://pbase.com/9146gt/image/23962411 the Ernst Seiler factory 914-6 GT https://pbase.com/9146gt/image/75088570 the factory Daytona Winning GT https://pbase.com/9146gt/image/88693847