Thanks Pat:
Do you know if this bulb was also used in early Fords? The Graham uses a headlight that is built into the fender and is an unusual, almost square shape so a sealed beam would not work. I looked into using a square sealed beam as used in some late 60's and early 70's, but it will not fit behind the glass covers without extensive remodelling.
Do you know what is required to change from positive to negative ground?