I'm afraid "virtually identical" doesn't quite get it. I want to see the bare chassis without the shell to determine if it will do the job. Can't just throw away $ on just a hope. I already ended up with an old chassis without a PC board, mini-bulbs and out of sight wild gearing, totally wasted money.
I do appreciate the help.
Lack of info in your original post doesn't quite "get it", either. More info in your asking post could have prevented you from getting the wrong chassis. So, I guess I'll be the dentist, and let's see if we can pull some teeth to get some more info out of you. Do you prefer Novacaine?
First, how old is the RS11 you have?
Is it an Atlas/China, or is it an Atlas/Kato?
If it is an Atlas/Kato, does it have two black gears between the motor and worm, with a small "X" contraption between them, or does it have a very long worm gear that extends from the motor to the truck tower?
If it is an Atlas/Kato, does it have bare metal wheels, or are they blackened?
If it is not an Atlas/Kato, does it say "Atlas China" on the bottom of the fuel tank?
If it does, did it originally come with knuckle couplers, or Rapido couplers?
If it is an Atlas/China, did it originally come with an LED headlight in each end of the frame, or did it come with a circuit board that runs the length of the engine with an LED on each end?
If it has a circuit board that runs the length of the frame, is the motor frame grey or black?
If it has a motor with a black frame, does it have brass contacts that run the length of the frame, or does it have a pair of wires leading from the frame to the trucks?
ALL those are variations of the RS11, which began around 1984, and shared the exact same chassis as the RS3, RSD4/5, RSD12, and GP7. Later models dropped the frame from the GP7, when they shifted production to China.