Hello whiteside,
both FSX FA-18C and CS FA-18D models will work fine, in P3D v2. The only thing to consider is that some LEX vapor and afterburner effects may not look as nice as in FSX or P3D v1.4, but that is just me ranting.
In order to properly transfer all that is needed to the new sim from you old FSX just copy the following folders, WITHOUT replacing stuff from the new sim (P3D v2 in you case) in case duplicates are present. Just go to the main folder of you old sim and copy the following folders: effects, fonts, gauges, simobjects and sound.
This is a simple approach. You could also look into each of these folders and copy only the necessary files for each airplane that are needed, if you know what to look for.
Note: Before you mess up your original P3D v2 installation, make a backup, e.g. zip the entire folder to an other hdd, so you can easily revert in case something went wrong.
In case you have A2A or FSUIPC stuff present you need to copy the content of your old modules folder too and register these addons in AppData>Roaming>Lockheed Martin>Prepar3D v2 under the dll.xml and exe.xml the same way as you did for your old sim.
An other approach is that you can create a dummy FSX folder, with an fsx.exe present and pointing Xload to that specific folder, where all its stuff will be placed. Than simply copy everything you might need from that dummy folder to your P3D v2 locations and it should work too. This is the way I usually prefer to do it, so one can actually control what is copied by the addons.
Additionally, in case you want to brush up your german language skills, you can find a very good artice on how to install addons without FSX present here, the best I found on the web so far, very detailed showing some very nice hints:
http://simmershome.de/prepare3d-ohne-fsx-mit-allen-fsx-addons-betreiben/Mainly it is done by creating links to files and folder from FSX to the new version P3D or P3D v2. It will give you also a good understanding how addons are placed within the sim.
Hope this is of some help, Peter