They were an option on all 70-74 Barracuda and Challenger. The 70-71 attached from the inside of the fender, so it was smooth on the top. The 72-74 attached with a screw that went down thru the top of the housing, so a Phillips screw showed from the top. I think the 72 and up are repro'd. But they all interchange for fit and wiring.,
On A bodys they changed to the larger style in 73. I believe the 72 E body used the same smaller housing as the A body did.
Im pretty sure 71 E was unique because they were all painted.
Someone does make the small housing chrome ones for 72 because I bought some for my dart. Just cant remember where I got them from.