An up rated clutch is one thing, but you don’t want to move outside the design limits of the M32 gearbox. For the higher output Alfa’s fiat moved to the F40 gearbox as mated to the 2.4 JTDM (200bhp 400nm peak) and the 3.2JTS V6 (260bhp 322nm peak), the M32 is used with the 2.2 JTS (180bhp 230nm) and the higher output 16v 1.9 JTDMs (150 bhp 320nm Peak)

From what I have read the M32 6 speed box was designed to have a max working load of 320nm, so pushing above that will not help its life.

The numerical designations usually indicate the maximum torque rating of the gearbox in newton metres. For example, the F40 gearbox is rated at 400 Mn or 295 ft/lbs torque; the M32 gearbox is rated at 320 Nm; the F17 gearbox is rated at 170 Nm, and so on.