I am trying to track down the cylinder seals for the gate (Gate lift cylinder). I called a reliance shop and the guy there said that its not easy to get the seals, and he would have to look back thru all sorts of old boxed infromation to find out the build and then go from there. I know the reliance body serial number is 921291 I know the rod diameter is 1-1/4", tube was i believe 18" long if i recall correctly and the tube outside diameter was 4".
Have you tryed a shop that rebuilds hydraulic cylinders. They could probale take it apart find the right seals.