Get the one that is cheeper OS V-spec or the RB WS7II either motor is great and I think that if you look around you can get RB parts just a quick and as cheep....Piston Sleeve and rod for either is $160.00 so the choice is literaly 50/50 I use a RB and have nothing to say but praises all around..RB makes a great motor..the V-spec I am still waiting for more data, from people were I live. That way I can make a good comparison. My friend has an OS and I have a RB we both do well neither is any greater but I do notice that the OS can pull away from me adn my RB takes the corners and the start almost every time...Hope all this helps...