I ordered a Victor Reinz gasket for my F54 flat top and N47 head, but, they had four different numbers listed! Not sure of the year of the block either, the numbers they had were for 70-74, 75-80, 80-2/81, 3/81-83. What were the differences in the years to require these different numbers? Isn't the HKS steel for all years? What one should I be getting for my setup? Thanks