Vents!

Big electronic devices like retro computers need to be cooled, and that means vents and grilles.  Finding suitable parts in 1/6 scale isn't that easy, so I looked to smaller scales... and found a set of engine deck grilles for a 1/16 scale Panther tank.  These are etched brass and have some nice bolt head detail on them.

The rectangular grilles are perfect for air vents on the front of the tape-drive cabinets.

Once painted and with a black wash in the recesses that should look pretty effective.