To make the radio come on with the ignition snip the lead on the jumper below the W101 label. This board is accessed by removing the smaller of the two covers. Then connect an ignition source to pin 3 of the 15-pin accessory connector. I think you can also connect the ignition to pin 2 on a remote head.
NOTE: - The above picture is misleading. This is the way the radio was when I received it from Ebay. To do the ignition mod the jumper shown cut in the picture (W107) needs to be intact and the one to the right of it (W101) needs to be cut. It's explained below but not all that clearly I guess.
Update - Connecting ignition sense through a remote head is a little more complicated, but nothing discouraging. When you connect an ignition wire to pin 2 of the remote head you are using a spare wire. This spare line stops at solder point 'A' on the main circuit board (the same board you mess with above). You have to solder a jumper from solder point 'A' to solder point 'B' in addition to the above mod of W101. This connects pin 2 of the remote head connector to the same circuit as pin 3 of the 15-pin accessory connector. This would also be a useful mod if you wanted a source of switched power at the remote head.
I believe the radio comes from the factory with the leads intact on W101 and W107. I bought this radio on Ebay and it came with lead W107 snipped, and I had to resolder it for it to work correctly. Battery power comes through W101. Ignition power comes through W107. Snipping the lead of W101 keeps the battery power from the turn-on circuitry.
Additional info: The two headers above these jumpers are the wires to the 15-pin accessory connector.