Best Mullard 5AR4/GZ34?

I'm looking at replacing the rectifier tube in my Modwright LS100 having already replaced the stock 6SN7's with Sophia Electrics. Is there a meaningful sonic difference between the various Mullard rectifier tubes? Should I be looking at NOS or newly manufactured issues? If NOS, which version (and how will I know I'm getting the "right" one) and what should I expect to pay? If new, which of these are the best sounding and most reliable? Advice on where to purchase or even offers from sellers are welcome. Your expertise is much appreciated.
The Mullard/Blackburn factory tubes, are the best sounding rectifiers out there. Forget about anything being manufactured today. The earlier/the better, but all Mullard/Blackburn factory valves are worth the money(regardless of the branding they ended up with, ie: Hammond, Bogen, Dynaco, RCA, etc). If you keep your equipment; the GZ34 may outlive you! ie: ( ( (
Metal bases, fat bases, brown bases, double getters, Bugle Boy, fake tubes.... It's enough to make your head spin.

In any event, seems that Mullard/Blackburn vintage late 50s to early 60s are the ones to get.
If the tube bears the RCA label,or any of the others mentioned, how does one identify it as a Mullard/Blackburn?

I have a few of the old RCA rectifier tubes from that era, and as old as they are, they sound much better in my SET amp than the one that it came with.

An Old Sylvania from the same era is also no slouch.
Mr L- Recognition of the variously branded Mullard tubes, comes mainly with familiarity of their internal construction and date codes. Here's some info on the coding: ( )
Thanks for sharing Rodman99999.
No Problem! Enjoy the music.