I have done about 6 600 heads to 50 combines, you need to do the hydralics, single hookups and you have to do an electrical update, ie either download new software to the ahc board or a new board, depending on the serial number, new cornerpost display and software, new elastomiser pad, and armrest software. All of this is avaliable as bundles....you also need to update the feederhouse drum cover of some machines.....