The Stovebolt Site Forums The Shop Area General Truck Talk GMC Parking Lights

jthuma94,
You might check this out: http://www.oldgmctrucks.com/page0030.html
The park lights I used for my '53 measured three inches in diameter which is right for '51 and later GMCs but the back of the light was as large as the pre '51 GMC lights. I was told they were backup lights from a chevy car. They look correct for my truck, but I had to drill the hole out bigger to fit them.
So I guess it depends on what year your truck is and how correct you want to be.