If you have the driveshaft with the ball and trunion u joint on both ends, remove it, swap ends. See if your noise goes away or changes. Before you remove it mark the flanges so you can replace it to its original position if you need to. These setups will over the years make one joint dominant, especially if your use and loading of the car never changes, meaning one will do most of the movement and work, the other will remain it a static position. Swapping ends will cause them to get out of their ruts and move through different patterns in different places along the trunion.
This might moderate the noise, change its frequency, or better isolate it's source. Or help to point you elsewhere for the source of your squeek.