[G3PIJpeter]

Another approach is to build an up / down converter from the 455 kHz IF in the receiver to the frequency of an HF ladder filter and then back down again to the IF. Many of us have shovelfulls of 3.51xxx TV crystals tucked away, from which a suitable selection can make a very respectable CW, SSB or AM passband. The up / down idea was described in a 1980s Radcom article and there were several others. However, if you do have a suitable Murata ceramic filter at 455, then it should be straightforward to fit it into an impedance matching amplifier (to make up the loss). Again, I seem to remember an article in Ham Radio.

And what about an outrider BC453? - there's more than one way of skinning a cat etc.

Peter