The gear cover from FG fits just fine, the same does the Carson Gear cover(I have both)

I had to do a bit of modification to the Carson Gear cover, else it hit the rear upper a-arm. That isn't needed with the FG Gear cover.

The Radio Plate on the FG Lepard Race is the same as used for the FG 1/5 on-road cars. Mine has room for 2 Jumbo servos for steering and 2 small servos for throttle and brake + receiver box.

Attached a pic of my radio plate, from when I was running 1 steering servo.(a bit dark)

As for throttle/brake servos, mine locks the rear brake without problems with the Hitec 645MG

Most people running hydro brakes, uses 2 servos for braking.
1 for throttle + rear brake, another for the front brake. That setup is also common with cable brakes, but some runs front cable brakes on a single throttle/brake servo.