[Hallicrafters] HT-32mk1 output tubes

[Will]

I just added a HT-32 MK 1 to my radio room and I have a question for 
the group.  

 was reading about the different version of the 6146 tube and was 
wondering which version my HT-32 requires?  the ones in it are marked 
6146 and have another number on them that includes 56, which I assume 
is the date code?  If this is true I assume they are the original 
tubes.

The output on 10m is down to around 25w (better on lower freq's) so I 
assume the tubes are getting weak?

Do I need the original version 6146 / 6146A or can it use the 6146B 
or 6146W?

thanks for your help

will R
W3WJR