I have it back in one piece
New rear diff internals with brass spur gear, metal driveshafts, 2 speed, 3s lipo, 1625 ESC. It took some machining and fiddling in drive line. No kidding those grub screws are serious issue as my shafts came apart several times during testing. I know I am overly excited with details as I am quite casual hobbyist.
Few problems took me by surprise - like ESC brake working in reverse and reverse seemed faster than forward. I had to switch motor wires and set throttle channel as Reversed.
Here is a photo of transmission servo clearing suspension links. Easy to imagine them interfering in out of the box layout.
I am quite satisfied with speed range and overall snappiness of the setup. On hardwood floor I could almost drift. But I may look for a better 370 motor with better magnets. My magnetized screwdriver was able to pull screw of off motor casing. I think that means good 370 can have higher top speed and better low end torque over stock one.