This forum is dedicated to discussions pertaining specifically to the Motorola ASTRO line of radios (those that use VSELP/IMBE/AMBE), including using digital modulation, digital programming, FlashPort upgrades, etc. If you have general questions please use the General or Programming forums.
You need the W3 HHCH obviously, and the W3 interconnect board. There are other small parts you'll need too, like rubber gaskets, the flange that covers the KVL port, and some assorted screws.
A W3 s-record would also be quite useful.
If you plan on doing an extended remote install, you will also need the control head extension cable.