ARC Ref 3: Tung-Sol 6550 in power supply?

I have sourced a new production Tungsol 6550 from The Tube Store in Hamilton (Ontario); I intend to use it in the power supply of my ARC Ref 3. Has anyone had any experience with the Tung-Sol TS6550 in the Ref 3? Have you compared it with the original Winged "C" SED 6550C shipped by ARC with this
line stage? Preferences? Reasons?

See:
http://thetubestore.com/tungsol6550.html