Reading replies to some posts can seem foreign until you realise how many different variations there are amongst the different models
My KZH100 still had the original Japanese unit and didn't have a amp that I recall but either way it was usless here in Australia so I pulled it like a sore tooth and replaced it with a double din GPS/dvd/cd.
I do remember that there wasn't a whole lot of space to fit all the wiring including the adaptor and the head unit but I also ran RCA stereo and video cables from the connections in the rear of the head unit to another screen in the rear of the van.Managed to get it to sit nice in the end.
Should it come to you having to change the head unit, I found my adaptor at Repco for about $12 and as there are 2 for Toyota Hiace you are better off if you can see it in person to make sure you get the right one. What you need is either the AERPRO APP0140 ISO Adaptor or AERPRO APP0141 ISO Adaptor...... I don't recall which one I used.
and Yeah!!.....Super Customs are AWESOME!!!!