One thing.. He doesn't have any weight on the frame right now to make the panhard bar go into place... I think it will be right once the weight of the car is all in place..And yes the panhard bar needs to be as long as you can make it.. You can move the bracket over the rear end (center) to right inside the frame rail over the axle on the drivers side..
As far as the pinion changing.. I don't see that happening with the way the bars attach in front and in the back of the rear end..With them long arms, It will not travel that much in the arch to change it..
I think your doing a great job,, The only think I see is, The frame came out great... (And don't take this the wrong way but), The notch is really ruff.. Doesn't look like the same guy did the frame and notch.. I know you still have to clean it up... But it's over built... Other then that.. It's looking good and I can't wait to see the rest..