A bit late in the day but the Pyramid Parts are excellent and come with a better bottom seal as part of the kit. Good branded bearings as well at a decent price - NTN or Koyo.
It's worth measuring the original bottom bearing height plus any spacer then ensure the replacement part is not taller at the bottom but close enough to avoid either running out of thread at the top or it not clearing at the bottom.
If you get it wrong there are pullers that will enable you to remove the bottom inner race without damaging it
I did not use the top seal they provide as it left the top thread a little short. I used their kit on my 500.
On my 400 I was not aware of a suitable kit - the one I bought ended up as a hybrid with a taper roller at the bottom & a plain caged ball bearing type at the top as I was out of thread. The Pyramid kits show the sizes available plus there is some fitting guidance though the site is a bit oddly laid out.
Others here have found the Pyramid kit for the 400 fits - I think Oldchuffer used one on his 400.
