Tail light question

[Muscle racer]

I was riding yesterday, when I hit a bump.   At the stop light, I looked back and noticed my tail light was gone! The way I had it placed was pretty close to the back wheel but it never rubbed it.  Until yesterday. I turned around and went back but never found it. I have a 78 750k. The tail light was the original, so it's big and square.  

My question is, I'm trying to replace my seat with a smaller seat and wanted a smaller tail light. I looked on eBay but I wanna make sure it fits.  Do all tail lights have the same green/brown wire connections? And the ground piece? Do newer LED lights have dif wireing?

Does any one know any websites that sell pretty cool ones.

Thanks in advance

[TOOLS1]

Dime city has a pretty nice selection. Tail lights will all have 3 wires, but they might be different colors. You might need to connect them to a 12 volt source to find out which is which. The one that glows the brightest is the break light. The ground should be obvious. It will be connected to the metal bulb holder.
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