Personally I wouldn't use Tamiya's photo etch. It's made out of a material which is way too sturdy to handle decently. If you want to use photo etch it's better to score an aftermarket set made out of brass. Often they are cheaper as well.
Parts Nos. 1–6 are the covers for the cooling air intake and outlet, under the sides of the engine deck (intake left, outlet right). You can see them on this photo, lying flat on the mudguards under the outlet grille: