You have got the right idea.
I doubt you find anything that is a perfect fit right out of the box.

Do you want it to look original? Here is a picture of some 4" LED lights on my 1 ton. I plan to use the exact same setup on my 6400. Although I may trade the taillights for back up lights and then move the taillights out to the corners of the bed.

http://rides.webshots.com/photo/2970880650080251109semNwf

Grigg

•1951 GMC 250 in the Project Journals
•1948 Chevrolet 6400 - Detroit Diesel 4-53T - Roadranger 10 speed overdrive - 4 wheel disc brakes
•1952 Chevrolet 3800 pickup
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"First, get a clear notion of what you desire to accomplish, and then in all probability you will succeed in doing it..." -Henry Maudslay-