Thanks for the suggestions. It's more of a mechanical clunking than a clicking, which makes me think it's the UJ. And it turns out it's the Ford/Getrag MT82 gearbox, not a Transit gearbox. I'm going to get it up on a friend's ramp on Saturday so we can have a closer look.
Even on a lift the boards on my car were too close to get a grease gun in. Hence the hole in the tunnel.
If you can't do it let me know and I'll post some pics
