Looking to add can lights

[black_k5]

I picked up a k20 a couple of months ago and I really want cab lights. I know I don't have the raised panel roof but I bought a set of aftermarket high hats that has the bulb assembly completely above the roof so theres no issues with clearance. I have read many threads but have not found anyone that has the measurements from a cab that has the factory cab lights, only for the Yankee 77. If someone could measure it or if anyone has a truck in the Philadelphia area that I could measure that would be awesome.