Cab Roof Lights

[prg machine]

I'm interested in putting some clearance lights in my K-20. I have several questions:

1 With a conventional roof skin, none raised, is there plenty if clearance between the roof skin and the cab inner panel to drill mounting holes and instal wiring?

2 Can someone give me some dimensions from the Center of the cab, where the center light mounts to the two adjacent lights that are fairly close to the center one, and also the distance from center, or outside edge of cab, to the center of the ones closest to the outside.
The distance back from the front edge of the roof also.

3 Are the Pacer lights a Chromed Plastic base or the pot metal, like the original? They seem awfully cheap to be the real deal

4 NAPA sells them, but there over 50 dollars each and they don't indicate if they're plastic or not
I'm also considering E-Bay.

I'm talking about the Tear Drop style, something 77s I think they're called for the original style.

Thank you!!