In order to lock up a motor that's not had water intrusion into the cylinders, it normally has to be running and the action of failing for whatever component fails is not something you'll miss. I suspect that you've boogered something up in the reassembly after the clutch pivot ball fix. Step back, take a breath, ignore trepidation over what you don't know, then work the problem. If it'll turn a few degrees then it's not hopeless. You could easily have the tranny misaligned causing the starter gear to bind up on the flywheel ring which could render the symptoms you're having. Check oil and water for signs of evil. If you don't see obvious sign, move on to the reverting of the trans/clutch change and drop the transmission and make sure the starter isn't stuck into engagement with the flywheel. Then rotate test again. Calm. Calm. Calm. Get your frustration hat ready but don't start out wearing it, it'll only cause you to make more mistakes. We all bone a reassembly once in a while.