yeah the heads and cylinders are the same length.
but there are a lot of variations to the big bore swaps.
what model is the 110cc 1P52FMI? or something close ?
if it is,
the bore is 52.4mm across and the stroke will be 49.5mm, it has a 13mm piston gudgeon pin, and is a 104cc (107cc cast into the cylinder of head)
one 125 has a bore of 54mm, and a stroke of 54mm, and has a 14mm gudgeon pin in the piston, and this is a 123cc engine (commonly known as a Lifan 125)
there is another couple of variation's,
one that has a 52.4 bore and a 57mm stroke, and the piston has a 13mm gudgeon pin in it, this is a 122cc engine (124 cast into the engine)
and then there's one with a 52.4 bore, 55.5mm stroke, it has a 14mm gudgeon pin in the piston, it is a 119cc
so you need to know that the new bore/piston and gudgeon pin will fit the 110
using the bore off a 125 engine with a 54mm bore on the 110 (55.5mm stoke) will up the 110cc engines' capacity to 127cc
and it will give the engine a bit more torque, a noticable difference in power, the 110 gearbox will be fine.