You'll probably have to try and "open" the clamp part of the joint with a big screwdriver or chisel. And lots of penetrating oil. The OEM u-joints are a common failure area (excess play). New U-joints are recommended! You can slide the shaft up towards the firewall if you loosen both u-joints with everything else in-situ. I didn't say it was easy on a rust bucket like this though. Slather in anti-seize once you put it all back together.