The Super Pershing takes lots of work in the modelling skills dept. A considerable amount of sheet styrene and scratch building the huge counterweight on the turret overhang and added armor will keep you busy. The Super P's T-15 gun is twice the length of the M-26's M-3 but all you need to do is cut off the muzzle brake, pull out the metal barrel a bit and slide a second Pershing gun tube on it, seal the joint and it's done. (This kills the BB game however.)The equiliberator springs on the turret have to be scratch made as well as well as the stowage brackets on the fenders, but that's just plain modelling. A set of impact's T-81 tracks is a must and it just sets the super Pershing off in a class of its own. I am now having my Super-duper set up for IR combat and will give it a good test in March.

There are plenty of good photos to guide on converting;
Dick Hunnictt's Pershing, Osprey-Vanguard's M-26-46 are a good guide.