I purchased a used 1" spacer to install on my Nordic Heat with a B1X. I ordered the 2 big o rings and 1 small o ring for each side, but I noticed the factory diagram also shows a speedometer seal 26-805344. Do I need one of these on each side of the spacer?

If the speedo is hooked up---yes for sure.
I would do it either way. Its only a few bucks.

Thanks. They arent easy to find localy