The best shell is the "BEAST" from SPX, they are nearly unbreakable or the GM #24221190 revised sun shell kit has worked in most cases, however the sun shell is always going to be a concern. The revised GM sun shell rarely fails and if it does, it's most likely to strip the teeth off the sun shell.
The pumps for the 4L60E can be found in 10 vane and 13 vane versions. Best to use the 13 vane pump, the pump does not have a higher pump volume than the 10 vane pump. Instead, the number of vanes was changed to alter harmonics that caused the rotors to break up. You'll also want to make sure that the splines on the stator are in good shape and replace the boost valve with a Sonnax valve or TransGo, as these are frequently worn out. The valve and sleeve can be replaced easily for around $50. Oversized (0.490" versus the stock 0.470" or 0.420") reverse boost valves provide a moderate increase in pressure, and are a good addition to any 4L60E.
Also remove and discard the 3/4 load release spring assemblies (5 small rectangular spring assemblies installed into the input housing, on the outside of the clutch pack). This really improves the 2-3 shift.
The Low/reverse piston which is the large piston at the rear of the transmission's internal components. Never reuse casting number 8681725, as it is known to have durability problems. Replace it with one that has casting number 8685550 (GM part number 8685549), which is a much stronger piece.
Since you are inside the transmission, replace all the electrical components (wiring, solenoids and switches) inside, especially the variable force motor solenoid (electronic pressure control) valve solenoid.
Keep us posted and be safe
Molson02536
