Used a Shugart 360 which originally came out of another Wang PC.
Used it to write DOS 2.1 disk image, changed DS to '1' instead of '2', wired it up.
It boots fine but I need a screen
It seems once MS DOS starts, it's not interested in using the serial port as an output device any more. I would do CTTY COM1 - but this version of DOS is very different to what you see on PCs. Looking at what I can off the disk, it starts an alternative to COMMAND.COM - uses a special Wang interface instead - I could get it to run COMMAND instead - but then what baud rate do I use? (There is no MODE.COM) Does CTTY work? Do I use COM1 or SER1 as the device name? etc etc - lots of questions.
I could likely wire up a Multisync display to the plug, but preferrably need a Wang monochrome display (from a terminal or Wang PC). I also don't have a Multisync - seems to be rather hard to find. It's 800x300 @ 60Hz - so HSync is too low for most modern displays, and VSync is too high for most older displays.