I restored a 1973 Interclub this past Winter. They were Gitanes entry level racers, not the lightest bike around, about the same as a comparable Peugeot with the carbolite frame but the quality of workmanship is much better than Peugeots in my experience. I was pleasantly surprised at how nicely the bike rode.
The wheels probably are tubulars. Changing to 700c clinchers would be an advantage in some ways i.e. easier installation and flat fixing on the road but these bikes were designed for tubular tires and the ride, with the light tubular wheels and tires, is way better. There are also a lot of reasonably priced tubular tires available fron online cycling shops so don't dismiss tubulars too quickly. Depending on the age of your bike the rear axle spacing will be either 120 or 126mm so you'll have to take that into account if you shop for new wheels.