You Have PM
Regarding Baz's/Laurent/marinaltlas' comments you will have to go with a historic registration, because you can't have a Certificate of Conformity (COC) for it.
Simply, they don't conform to modern standards, so with no CoC there is now no choice of a 'normal registration' for vehicles over 30 years old. I don't know when Baz's mate or Laurent may have done the importation, but today, now that you have to use the centralised ANTS system, ANTS require a CoC issued by the manufacturer. None of your vehicles do and the manufacturers of those marques would not provide you with any documentation.
I will have to chat with marinatlas when I see him next, because I don't understand fully his comment, but I think perhaps he has bikes that were already registered in France when he purchased them or the major parts of them, or registered at a Prefecture before November 2017 when the ANTS system started. Different rules apply to already registered vehicles compared to imports, so I believe he has not applied to move them to vehicule de collection, which in his position I would not either!
Once a vehicule has the document, the 'Carte Grise' as it is still called by most, you are transferring a registration (immatriculation), this is now also done online, the vehicle being transferred should have a 'Controle Technique' (CT) with more than 6 months to run (if applicable) and the seller will need to log onto the system to complete the 'cession' document, which he needs to do to stop legally stop paying insurance on the vehicle, and you need him to do to register it. But these process don't apply to imports, or you.
Getting a Carte Grise issued for an import is a different process needing different documentation including the CoC, and with a vehicle like your Land Rover an inspection by your local CT, and in case of modified or non-conforming vehicles, also by DREAL! In truth, if you can live without your Land Rover, store it is the US, or sell it. Motorcycles are not yet subject to CT because the law due to come in today has been frozen!
You can of course ride/drive your vehiclule de collection on organised 'Balades', which is why many clubs organise them, but you can also test your bikes!
And it is amazing how much testing you need to do, and the places you need to go to, to properly test your bike!
I live in the wilds of Normandy, seriously, who is watching?