RE: Engine replacement for Force .26
There is no reason why it shouldn't fit. And it is much better to get an engine without a pullstart.
If you want it cheaper, then the OS RG without pullstart is only about 100$. I have that one in my LX Comp and it is a great engine.
But the Picco .26 or .27 gives a lot of power if you don't need it to be racelegal.