[Amps] Can I run 4-400's in TL922

[vk3ym at iprimus.com.au (RICK COLE)]

Am I able to use 4-400 tubes in my TL922 amp...I have just been given 10 of 
these tubes NIB and was wondering what I had to do to run these in place of the 
3-500's if the need arose where I had to change them out...It would really save 
me a lot of dollars to be able to do this..Can somebody advise what is involved 
with modifying or are they just "plug-in and go"..The 3-500's are the originals 
and are well over 20yrs old...nothing wrong with them...I am just curious for 
the future..
    Regards  Rick