+1 on tubular tires for the existing wheels. This will be your lowest cost option to get it on the road.
27" clinchers will be too big for the front brakes on a TdF. If you go the clincher route, use 700c wheels. The rear will be 120mm OLD.
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72 Fuji Finest 72+76 Super Course, 72 Gitane Tour de France, 74 P-10 & 79 Tandem Paramounts, 76 Grand Jubile,84 Raleigh Alyeska, 84 Voyageur SP, 85 Miyata Sport 10 mixte 89 Cannondale ST400 and a queue