JDM fender mirrors
 

https://cimg8.ibsrv.net/gimg/www.rx7...340b03c6de.jpg
I did just buy this car and will build a rallycross car out of it.
I might sell the JDM fender mirrors if I will get a good bid on them.
How much can they be worth?
I do know that they are rare...

What you should do is remove them and take note of their condition, then go from there. It's hard to put a price on something when you don't know it's condition.
For me, I see similar inexpensive mirrors on ebay, so my vote goes to pricing them similarly. Not everyone is willing to drill a hole in their fender for a mirror they have to get out of the car to adjust and readjust.

Regarding the mirrors, I would look around at the current market and see what
other sets in similar condition are selling for. Once you have that info, you can set a price range that you would be comfortable selling them at and list them for sale. You can use the marketplace section here on the forum if you have a set price or you can try eBay if you're looking for bids. Here, we can only help you determine the approximate value so that you can list tem for sale elsewhere outside of the tech section.

Ugly

I thought only the 79-80 came with that style mirror .