Head - Galoob Unifighters
Arms - Crankcase
Torso - Galoob Uniighters
Waist, legs - Lift-Ticket
Helmet - Sgt. Savage
Backpack - Tiger Force Duke
Binoculars - Sneak Peek
Submachine gun - Marauder Inc.
The first customs I ever posted publicly were two versions of Duke. Some time ago I got a handful of Joe-like figures in a lot of fodder I bought, and was able to figure out that they are Unifighters from Galoob. Anyway one of the heads just screamed Duke at me: blond and square-jawed, and fortunately not smiling like a doofus as in the original figure. So I knew I had to make a Duke out of it. Actually, since I had two of that head, I decided to make two Dukes.
Unifighters are very slightly larger than your typical Joe, but Joes often have slightly large heads for their bodies so there's not really a problem there. But Unifighters do have a significantly larger ball joint for their necks than Joes do. So for this Duke, I used a Unifighter torso, and for the other I trimmed down the ball joint to fit a Joe torso. I did have to trim down the shoulders on the Unifighter torso, otherwise it would have looked pretty goony with ARAH arms.