I did all this conversion to my D15B auto manifold. It felt kinda MacGyver seat-of-your-pants while I was working on it. Just measure where ever you can, drill pilot holes, don't drill too deep (put tape around your drill bit so you know where to stop) and you'll be fine.
The first IACV hole is already there - loosely bolt the valve on, angle it so it looks square over top of the raised area and tighten it down. Use a pick to mark where inside of the hole meets the manifold. Remove the valve, center punch, pilot drill, drill, tap. Put some grease on the gasket of the IACV, thread the bolts in a couple turns and slide the IACV down to make a grease-stamp on the manifold. Take the valve back off - the grease shows you where the gasket needs to seal, and where to center-punch the air passage holes. Be careful not to drill or scratch up the grease-marked areas or the gasket won't seal.