An AADE design for a suitable third order bandpass filter, with 8kHz bandwidth and allowing a compromise 1dB ripple  suggests image rejection at 125kHz will only be around 30dB.   (Top coupled capacitor  design, so low side rejectino is better than high side)   Not sure what signals are down there to get through, and a highly resonant antenna will help a lot more with image rejection - but if its for a grabber, you're probably going to use a broadband active antenna.

Can't make out much else from the web page photos, and it give no specification.  But  such a simple converter concept can't go hopelessly wrong, if you accept the limited image filter that would be achieved with three tuned circuits

If I were to try that approach, I'd got for an IF of  15 - 19kHz, at the top end of  normal soundcard coverage, so bringing the image down to 105kHz and making it easier to filter - although there you would just be creeping into LORAN area.

Andy  G4JNT