A crystal for 5 MHz would be OK - 4
MHz would come up at 1000 kHz on the dial.

Peter-

With high-side injection wouldn't the dial tune backwards? 4000khz would
appear at 1000khz, but 4500kHz would appear at 500khz on the dial.

If Tony can adjust to the backwards dial, I agree that a 5000khz converter
crystal would be the better choice, since it might be easier to filter out
images at 6000khz than images at 2000khz when using a 3000khz crystal.

73, Fred, K4DII