transom seal kit differences R drive

[NWVintage]

So, I'm replacing all of my bellows and whatnot. Discovered a hole in the water hose and decided to just do the whole thing. I am looking at a few different kits online and have noticed a difference between drive seals in kits from different sellers that claim to be the same kit (use the same Merc PN). The difference is in the drive seal. Some have 7 holes and some have only 6. Mine has 6. Is that 7th hole there to provide compatibility with more models but still compatible with mine, or is it incompatible with mine?

Also, has anyone made the switch from exhaust bellows to exhaust tube and have any input?

Finally, my gimbal bearing has no play and looks to be in perfect shape. Do I bother replacing it?