1928 Buick Mclaughlin cyl head

[B. Verstege]

Looking for 1928 Buick McLaughlin 6 cylinder head,  casting number 210586.  Found a 1927 head casting # 201706, not sure of interchangeability. Any input on  these heads would be greatly appreciated.  This head should be what they call a master six cylinder engine. The head length we have is 30 3/4" and apparently there are 2 different lengths of these cylinder heads and also the water cooling tube length changes around that era. This 1928 car is a right hand drive that was made for the Duke of Windsor when he came over to visit Canada in that year.  

Thanks 

Ben