hi, im about to change the headgasket on my 7m, and instead of putting my 200000 mile head back on im going to put a better condition head on. i got this head with my parts car, it looks to be in good shape, but im taking it to the machine shop soon anyway to be cleaned. but i noticed that it only has three exhaust manifold studs in it. do i need to buy one of these heli coil kits and replace them all? or can i just buy 4 new studs and put them where the missing ones went?