the zinc kits that are for the 03' and newer B3's come with 2 cavitation plate zincs.

03 and newer you would use service manual #39, which is the broken into 8 separate manuals, and it also tells you the serial number break for the different internal oiling systems, you cannot mix and match all of the uppers and lowers.

You real sure about that ???
I have a 2015 Bravo XR upper and about a 2000 B3 lower (only has one cav zinc) and has been working just fine since 2015

100% sure, just got back from merc factory training, part of the class, I'll see if I can save the page out of the training guide and post it.

old (88-93) and intermediate(94-99) cross over, the 2000 and newer are the "new design" and only work with new design

I don't actually know what my lower year is. I rebuilt it some years back and it had 2 seals on each prop shaft and I changed them to the single double seal. Some of the numbers matched up to manual 11 and the rest was in manual 28. This was not a two piece lower

the oiling on the b3 has always been the same. the lack of oil circulation was only on the very first b1 drives. you will rarely see one as they only had it for a year or two in the 1988, 1989 era. the uppers were redesigned in 2000 to a different gear and bearing in the tower. in 2003 they changed the case on the b3 lower for an additional anode above the props and drilled the shaft for an anode behind the prop nut. the shaft seals can be updated any time work is done to the one piece style.