In researching a suitable filter, I found mention of a possible problem using a low pass filter. A filter is required to keep the radio legal. The 2nd through 4th harmonics are passed right through. This modification will indeed make it transmit on 472 kHz, but the problem is that the radio’s final amplifier filtering is ineffective since the 160 meter low pass filter in the radio is used.

The North American version of the Icom IC-7100 can be easily modified to transmit in the 630 meter band by removing a couple of diodes on the bottom circuit board.