If they are like mine, the pistons should be good, and the springs too, unless a lot of moisture got inside. Of primary concern is that the bores are smooth and round where the seals fit. Up in the front, even where the pistons slide, is less critical. Water got in, and the kart I am working on sat for a long time, causing some corrosion in the front, ahead of the pistons. Not a functional problem!
Again, if like mine, all you’re likely to need in the way of parts is a pair of rubber cups. Guess what? They are a standard automotive replacement part, originally used in drum-style brake cylinders. The masters should be 7/8″. While I do appreciate all that kart shops do to support the sport, I have an issue with pricing on stuff like this. Even at a local NAPA, I can get them for $2 each. Picked up two sets of ten (10) on eBay for $21.98, with free shipping. That is $1.10 each. Nice that they also fit the front (cast) calipers on my old kart too.