Historical vehicle registration information is unfortunately not held by the Archives. The Kithead Trust Transport Archive may be able to help with this topic of research.
The following guide will provide information on historic vehicle registration numbers, where they correspond to, and - if the records have survived - where they are kept.
We do hold one Motor Car Fees Book (ASKcty/14/3) for Kincardine County for 1949-1951: this records the payment of fees for licences, and does record the licence number of the car.