I would try to keep things as close to their original size as possible (openings, lens distance, etc...) and you MAY be OK.
That's what this board is all about though--buy something, tear it apart, and see if you can get it to work again.
Just so that you know, the jack-in-the-box I had at age 4 never was quite the same after I got to it.
I did find out how it worked though.
AND, the giraffe with the spring coming out his butt that would shoot across the room at my sister after that WAS kinda neat.