According to "The Dodge Story", the Spitfire head is a higher compression head used on the 230 ci engine in the last few years of production. I think the engines using that head were rated at around 150 hp.
They were supposedly available as an option as early as 1949, but that isn't confirmed in the book that I have.
There may have been a Spitfire head available for the long block motors as well.
