Rims
 

I have recently bought a 1986 FC coupe. It has the basic 15" rims which are not particularly attractive. Is it possible to interchange wheels from the FD . Also i have seen a second hand set from a Mazda 3, would these fit. They are Zender 5x114.3 15".

Generally, yes, if the bolt pattern are the same, they should fit. The FD wheels will almost certainly fit on an FC if they're both 5-lug.
However, your FC has big brake calipers in front, which the Mazda 3 wheels may not fit over. So, you also need to check what the new wheel offset is, which (to a large extent -- but in conjunction with spoke shape/design) determines the brake clearance.

Have fun!!!

If you’re considering OEM FD wheels as mentioned they’re 5 lug. 16x8, + 50 off-set.
You also want to check the back of the wheels....look for the bell-shaped casting:
https://i1126.photobucket.com/albums...psuzzq26c9.jpg