Well according to my records that model number comes up as 1980-1981 or an 1982-1983 Commando.Either way we can work out that it is a full crank engine.So in that case re-boring (I think) would just be a waste of money as there are still plenty of good second hand ones around.Then you've got the big hassle of finding a new oversized piston.If they are the same engine then they are very easy to change over without special tool.You can (if you have problems putting the piston back in)get a ring compressor to help with that.I can (as I'm sure most people can)put it back in without it.Some do choose not to as sometimes it can be more of a pain,I think it is anyway.If your not sure if they are the same just pop up some pictures and I'm sure others as well as me can help identify them for you.Hope this helps.
