Hi Eddie. The transmission in my MKIV is a stock auto, originally built by toyota. The valve body has been modified and a precision 3800 stall converter has been installed, but the transmission has never been gone into. It is out of a different car and of unknown mileage, but I think it is a very low mileage transmission. Many of the "built" transmissions you see out there are just a basic rebuild with the exception of the billet forward piston(which isn't really needed on a stock twin car). It is the valve body modifications and converter that will improve how the car will perform. If you have a healthy low mileage transmission and are only looking to have a little fun with the stock twins, I don't feel a "built" trans is needed if you are capable of pulling and installing a valve body.