I am currently on a site that has a disconnect with 3 different fuses inside. How would you model this?

Got a pic? Like 3 different brands but same amp and type or 3 different types or 3 different amp ratings or some combination of the above?

For example, (from memory) Buss Frs-R-100, Gould trs100r and Littelfuse FLSR100? All are the same curve. Pick one.

I modeled them below. All 50A, curves are slightly different

As long as they are all RK5 fuses with the proper voltage rating, I generally just pick one and put a note on the drawing that the switch has fuses from different manufactures. If you have RK5 and RK1 fuses in the same switch I will model with the RK5.

This. ^^^^^^