1970's Gitane Gypsy: Brakes and types I can Use Shimano: ULTEGRA R8000
Long reach brakes are often used on bikes designed to fit larger tires, or if a bike that was built to fit 27" wheels (iso 630 mm) is adapted to 700c (iso 622mm). Based on a quick Google image search, it looks like you might be in the former category, in which case the short reach r8000's probably won't work... But you should measure it yourself. 

To tell which brakes will fit your frame/wheels, you need to measure the distance (in the up-down axis) between the center of the bolt that holds the brake to the frame, and the center of the braking surface. If you have brake calipers that work, and you're not changing wheel size, you can just measure your caliper from that bolt to the center of the brake pad. It's kind of a rough measurement because you have to hold the ruler straight up and down and just eyeball it. 

As long as that number (the "reach") is within the range of the caliper you want to upgrade to (Shimano ultegra r8000 is 39mm - 49mm) it should work. 

Also see this answer: https://bicycles.stackexchange.com/a/29362/37296