We extend to you a cordial "WELCOME ABOARD !" Come on in, make yourself at home, we are a friendly group of enthusiasts, and we also appreciate the classic Chris Craft Roamer, Corsair, and Lancer boats too , as they are all on the same family tree and share much in common !
I offer my repect and admiration for the aggresive restoration project you are undertaking in France, and compliment you on the quality of the work I see in your photos. This is not the first time we have heard about the strict regulations on your side of the pond, and yes, I think it is just fine to install a new Volvo or Mercruiser I/O in the boat.
With a reliable new power system like that, you will have a new boat, in a unique and very classic fiberglass shell. I dare say, you will even get a second look from the guys driving a Riva. They may not want to be seen looking, but they WILL LOOK, ha.
I hope you are able to keep the cabin and controls looking as reasonably historical as possible, and let people guess what kind of power you have aboard. The hull is too rare to do a custom job. The boat will probably take whatever sane power is available. Just be sure to anchor everything down properly and transmit all the thrust from the outdrive to the motor, and not to the transom.