The V-belt pulley on Syncros is the same as on 2WD models. However, on Syncros Volkswagen fitted an extra collar (025-105-248A) on the sealing surface of the pulley that is designed to work in conjunction with a special Syncro only pulley seal (025-105-249A). This metal sleeve, and a corresponding extra lip on the special Syncro only seal, acts as an added barrier against debris and moisture for severe driving conditions, like when you drive your Syncro through 4 feet of water for example. It is overkill to say the least.
Most other engine builders don't put the front pulley on for their customers. However, it is not possible to ensure that the engine is properly assembled and sealed-up unless the pulley and seal are installed, and the fastening bolt is installed to the proper torque. This practice might cause a little confusion, but it ultimately leads to a superior quality rebuilt engine.