The Dynaplates are not needed unless still part of a radio installation.

The lightning protection, i.e. the mast, stays and main shrouds as well as the AC ground are normally connected to a keel bolt, or to the metal mast step.

It is advisable to choose a bolt in a dry area, if this is not feasible the suggestion is to install a stainless flat bar extension from a bolt up to a dry area, and make the connection there in order to reduce corrosion problems between copper and stainless.

Pls note that the electrical conductivity of stainless is about 1/60 of that for copper, and therefore a correspondingly bigger cross section is needed.

The DC system is a two-pole insulated return type, and does not need to be grounded, but probably is if the negative pole is connected to the engine block.

Or do you have an insulated engine electrical system?

The AC ground can be connected to the same keel bolt, but in case there is a voltage difference between ground line and water you should consider a galvanic isolator, or an isolation transformer

Kind regards

Lars