Overdrive Transmission for 630 HP motor
The diesel guys have been running the 46RH/47RH/48RE behind high horsepower/high torque diesels for years. With the aftermarket hard parts that are available to replace the weaker parts OEM ones yours has in it, there is no reason to look at other OD transmissions. Do a google search for those companies that modify those transmissions and see what they might have to offer you. One company I recall dealing selling those parts to was called Farm Boy Diesel.