D640 vs D640-B? Is there a difference?

[smseely]

I have a G6200H with a D640 16 hp kubota diesel. I have been looking for a workshop manual and found one for the D640-B. Is this the same motor or slightly different? I figured it was the same motor but instead of in a G-series tractor, it was in a B-series. Let me know if you have an answer. Thanks. Scott