You may want to consider using the stock 8-blade plastic fan from the TR-6. It is lighter, moves more air and is undoubtedly better balanced than the original four blade fans. The part should be easily attainable through Moss or any number of other vendors; I purchased one as recently as this past spring for a TR-4A restoration. Its a straight forward bolt on part and I have used it successfully on several TR-4's and 4A's.