You have to have a special footvalve that will fit in 2" casing, not all 1-1/4" footvalves will go.
If you have a Goulds jet (common) then it uses a 1" footvalve. Sta-Rite uses 1-1/4" footvalves.
Whatever you do make sure you use a brass jet. Cast iron will eat out in some water conditions as it will be the only metal in the plastic well.