I've been trying to track down a good CRT monitor with a composite input for a while now to pair with some of my recent reproduction projects including the Challenger 4P. All in the name of authenticity. I finally found a Toshiba 13" CRT Color Television Model 13A24. While not from the 70s (more like 2005) it has a nice retro look IMHO.
On the Raspberry Pi 4, the composite out signal is on the 3.5 mm jack along with the audio out signals. There are a number of 3.5 mm jack to RCA cables available online, but for the most part they are setup for camcorders. The pinout for the Pi jack is slightly different. Here is the Pi setup.
Since I only needed the composite video and no audio I made my own cable with just the one signal plus ground.
To setup for composite out (NTSC in may case) I uncommented the following lines in the /boot/config.txt file on the Raspberry Pi.
# setup for NTSC video sdtv_mode=0 sdtv_aspect=1 enable_tvout=1
As can be seen above the TV works great, so far as it goes. I had forgotten how crappy text looks on a composite monitor. While a CRT is much more authentic, the "fake" monitor that I made for my Sol-20 Reproduction, using a period appropriate 4:3 LCD panel, is sure a lot easier on the eyes.