An older Sams tube substitution handbook that I have lists the 5AR4, 5CG4, and 5V4 as substitutes.
Check tube bias after any rectifier swap.
Great post! That's why each rectifier seems to have each own signature on the overall sound. It is not because it is NOS/Blackplates/GT/ST/etc. but because it changes the B+ and shifts the OP of the input/output tubes. For example, the 5V4 have a voltage drop of 25 V, 5Z4 at 20V, and the 5AR4 at 17V.
For the 5V4, I would suggest to check out the RCA ST type http://img518.imageshack.us/img518/4678/img4488td5.jpg
Wow thanks for the added info Hotsauce and Amandarae. My pre does not have a bias option(BEZ Q3b). I did swap for the CV 2748 mentioned and all is well. Perhaps I should stick with this tube for any replacements. It sounds good and trumps the stock chinese tube the pre came with. From my research are lots of 5AR4 subs out there from nos to current offerings. Stay tuned.