Hi,
You didn't say if you are working on the piston boot, or the Control Valve boot, or if it had 1 or both boots on it before.
There should be metal cast in the block that sticks out some for the blocks that used a boot and wire to hold it on. It goes around the bore in the block.
IH changed in the later years of Cubs, and didn't use a boot for the piston anymore, those blocks have very little metal sticking out, there's no way to put a boot or wire on them, I think.
I don't know which you have. If this is a 1957 Cub, it probably has the metal sticking out, it is about 1/4", and has a groove for the wire.
Someone could have put on a newer Touch Control.
Pics of yours would be helpful.
Below is a pic from TM Tractor, showing the piston boot and wire.