Cj1992 wrote im looking for an easy gearbox swap for my 740t ... im looking for a box that would handle a bit more power then the M46 ...
I'm focusing on your words '
a bit more power'.
After reviewing all the info in link (well done guys), maybe you just see if you ever break a M46 'P' or get bad noises, and if you do, then decide on options.
The downside to the big gearboxes mentioned is the weight gain and often bigger mass of a larger box. So if your reasonable with applying the power (not shock loading) the box you have could well be still suitable.
That said. a turbo engine is reasonably kind to gearboxes as the turbo kicks in at high rpm, compared to low rpm torque of a V8. It the shock loads (savage takeoffs and gear changes) and the torque twist from low rpm eg v8's again that does damage to shafts and gear teeth.
Supra W58 owner. W55 are the most common box. The R154 is a real big box, meant for twin turbo 6 cyl motors.