I have a 1986 rx7 non turbo. need to know what is the best spark plugs, wires ext. what is the the stock size of the air filter belt?

 

Use the factory spark plugs. For the wires use the blue NGK stock ones. For the air filter belt...I dont know.

 

just go to your friendly neighborhood parts store they just pull your make/model up in the computer and it tells them how many inches your belt system requires.. NGK for plugs 2 leading 2 trail, they have an L and a T on them and when you are looking at the side of the motor the Trail plugs go in the TOP

Trail - top
Lead - Lower

There are also some markings on the side of the motor with L's and T's to help you on your way..
Wires, I just got some run of the mill wires that were recomended by the computer at the part store too, unless you have some upgrades they should last quite a while