The LT77 and R380 are both strong units , but are not known for rapid changes.
The Mazda box and the T5 are both much quicker in action than either of the Rover options, which is why the racers favour the T5 (this was before the Mazda box became available.
Talk with someone like Brian Gateson at Techniques Morgan about the T5 , there is a bell housing available for this conversion.
I believe the Mazda box is used in the Baby Doll +4s and I don't think they experience many problems despite a hefty increase in bhp and torque.
