Firstly. i'm sure they are called rotors but if i got the name wrong don't hurt me

They're like 2 part discs, the rotor is the centre bit which goes over the wheel studs, and can be bought in various offsets to allow you to mix and match calipers etc, and then the actual disc part bolts to the rotor.

M12 thread, any good fastening place of hardware store. MAKE SURE u bolt them on with high tensile steel bolts!!!!!!!!!!!!

My set up i used standard discs as the calipers were already machined, i think the rotors will work out more expensive. You will also have to take into consideration where the brake pipe runs, when you fit up a 2wd caliper u will see the pipe connection points directly at the CV joint