@hiend2 - I suggest you talk to Brent Jessee, a good tube dealer. He'll be able to tell you what differences there are. Just google his name.
Raytheon 5751 Versions
Wondering anyone had experience with the wonderful Raytheons
I have the NON windmill Grayplates
What sound difference Are the windmill versiopns
I gather more lush mid band on the windmills.