An HDTV receiver box to insert in vintage TV IF strip?

[wa2ise]

Wonder if a HDTV decoder rigged to receive at the usual IF frequencies (41 to 47 or so MHz) could be patched in between the tuner and the IF of a vintage TV set? The box would create a new "fake" NTSC IF signal of the decoded HDTV channel. I don't know if the HD decoder would care that the received signal from the vintage TV's tuner is frequency inverted or not.

If this could work, your vintage TV would function similar to before, though you'd have to know where the HD stations really are on the dial.