150 barrel

Can anyone tell me what this cast iron barrel is originally from, I am thinking of re-boring it (and doing whatever is necessary to fit it to my GP150) and putting in a slightly bigger piston then have a play with ports etc.
http://i810.photobucket.com/albums/zz28 ... MG3643.jpg
http://i810.photobucket.com/albums/zz28 ... MG3642.jpg
http://i810.photobucket.com/albums/zz28 ... MG3641.jpg
http://i810.photobucket.com/albums/zz28 ... MG3640.jpg
Thanks in advance
http://i810.photobucket.com/albums/zz28 ... MG3643.jpg
http://i810.photobucket.com/albums/zz28 ... MG3642.jpg
http://i810.photobucket.com/albums/zz28 ... MG3641.jpg
http://i810.photobucket.com/albums/zz28 ... MG3640.jpg
Thanks in advance