3-500Z vs 3-500ZG

[Rod Fitz-Randolph]

Not sure about the 3-500ZG designation but I am referring to the
graphite plate 3-500s.

My friend, WA4VWR, needs to replace a 3-500Z in his SB-220.  He doesn't
believe he should just replace one single 3-500Z with a 3-500ZG but
he wants to know, if he replaces both of his Eimac 3-500Zs with the
3-500ZGs, will he get less than, the same as, or more rf output with
the exact same driving power?  It's a good question that I certainly
didn't have the background to answer.

Is there someone out there that may have replaced the 3-500Zs in a SB-220
or a Drake L4B that can answer the question for him.

Also, (on my own), is there only a single graphite-plate 3-500 manufacturer
and, if there is more than one, which one has the best reputation/track
record?

Thank you very much.

Rod, N5HV
w5hvv at aeneas.net