Still interested in Sean’s question on this - are there any known specs for that ‘box in terms of it’s torque capacity? I would wager it’s not made specifically for the RX and is used in other cars. My mate’s RX8 PZ was a hoot to boot around the twisties but had so little to with a quoted 160ish lbft max.
By contrast his twin turbo RX7 was a real animal but even then it was only c. 220lbft if I recall correctly.
I understand as a rule of thumb, decent manufacturers build in a 30-40% margin on the gearbox for longevity. Happy to be corrected / educated on that.