>I checked the Shimano website, the new part# for the 300
>Cardiff is BNT 2567.

i don't believe the website has been updated yet w/ the new schematics ... the part # you provided is for the older drag washer.

but to answer a previous question - yes, any older model cardiff can be retro-fitted w/ ARBs and dartaniums, though there are other le$$ expensive, more durable, & arguably better performing drag alternatives besides the darts, esp true if you'll be fishing in the salt ... }(