A simulation of pre-war 441 line B&W using n HDTV STB converter set to letterbox mode

[wa2ise]

using a Channel Master CM7000 set top box HDTV converter's luma output (from its S video output connector). Turns out that this converter box, set to "letterbox" mode, presents the HDTV 16:9 active video image as 3/4 the vertical height of an NTSC 4:3 (16:12) image. So, that would be 9/12, or 3/4 of 525i, which comes out as 393i. Which is 90% of 441i. Going the other way, 441i is 84% of 525i.

Okay, given the above math, we could overscan the vertical deflection of an NTSC B&W TV set to make the upper and lower black bars of the letterbox disappear. Or mask with a new bezel. Also overscan horizontally to make the geometry look correct again. This would yield a video image that would look a lot like how 441i would look on a pre-war set (90% is pretty close). A good cabinet builder carpenter could reproduce a period TV cabinet, and using one of those 5 inch B&W TV sets from China, make a good reproduction pre-war period TV set. Surely you didn't want to gut a genuine pre-war set...

To replicate the performance of an AM sound carrier (the FCC chose FM for TV sound after the war, for the new 525i NTSC standard, much to David Sarnoff's annoyance), you could take a trace of the baseband video signal and mix it into the baseband audio.

[old_tv_nut]

Two words:
Rube
Goldberg

...but interesting