To be honest mate, I would not change the rear end of a Kawada car for the SP12X rear end. I had a 12X for a while and had a lot of trouble with the bearing holders not staying on straight, causing lots of stripped spur gears. Also, a slight hit and you would have to replace the lower pod plate, T-bar and spacer, that was expensive! Stick with the Kawada rear end and you'll be fine.
Alot of rumors going around with the Serpent 12th car. According to someone at the Euro's, the car in the pics was a one off special, made up of parts from other Serpent cars. The rear end, nice as it is, was supposidly made many years ago by a Japanese designer, not actually Serpent at all!
Obviously, I don't know if what was said at the Euro's was or is true or not (rumor mill), however it was said by someone that would of known his stuff about that particular car. I think it looks great, has a couple of nice design features but we'll have to wait and see if someone from the company wants to come on here and let us know what the truth is about the future of the car.
Does anyone or has anyone seen or heard anything about the Xray 12th car? I heard a few years ago that they were bringing one out but it turned out to be a mini 12th scale 4WD Touring Car!