From what I can tell the NA and L67 throttle bodies are pretty close to the same. But blending it if it's different should be doable. You would still want to remove the throttle body blade and shaft to do it. I use 1" flapper wheels and and air die grinder and vary the grit depending on how much material I want to remove quickly. So an 80 grit running 80 psi removes it quickly but isn't too aggressive. 180 I use when I get close with flappers they typically leave a smoother finish than an equivalent grit on say a sanding roll or other rigid implement.
Jeff
