They are most certainly available in 4.56 from the dealer as I purchased a brand new one and retrofitted to my 85 pickup a while back.

Not sure what vehicles came with 4.56 ratio but here are the Toyota part #s for the complete third members;
- 4.56 ratio -> #41110-3D010
- 4.30 ratio -> #41110-3D080
- 4.10 ratio -> #41110-3D030