Engine Swap with older model

afaik the R125 started in 2008 (mine is the first year) so finding an 06 is likely to be either mis-labelled or something else altogether.

Any gen1 engine (2008-2013) ought to fit in any gen1 bike. Gen 2 (2014-2016 and 2016-2018) have some subtle differences which can be made to work but are definitely not a straight swap.