ZF and Getrag gearboxes
While the ZF should handle the power and torque, and is a direct bolt up to the Alfa engine, the disadvantages are its weight (there were even instances in other cars where block failures were attributed to the ZF), and the shift quality (the box was used in some light commercial vehicles, so this should give you an indication of its strength).
You can read more at the following site:
http://www.westnet.com/~mfrank/FiveSpeeds.html
In fact, my brother did some research on the ZF transmission, and found that in some of the light commercial applications, the gear selector was positioned further forward towards the bellhousing, so if you do decide to use the ZF, this may help locate things in the cabin.
Have a look at the following site (Transmissions section) regarding the different types of Getrag boxes available – you may be able to locate your ‘box in the list, and if so:
• see what model BMW it was fitted to (if the engine has similar power / torque to yours, then it’s looking good)
• check gearing, etc for your car (will help in determining what diff gears)
• determine what modifications you may want to do
http://www.metricmechanic.com/catalog/catalog.php
For my brother’s project,
http://www.alfabb.com/bb/forums/showthread.php?t=38223 he’s decided that if the synchros or longetivity of the Alfa 105 series gearbox is compromised due to the V6’s torque, he’ll source a Getrag 265 as it has a removable bell housing and improved synchros. With the Getrag that you have, just make sure that it isn’t the smaller Getrag 260 unit, as this would be too weak for your project (Getrag’s suggested torque application was 300Nm). However, they fit the Getrag 265’s behind V12 Jag XJS’s, so I would assume that it would do for your application.
If you're still after a source for Alfa Sei parts, feel free to PM me.
And if you do happen to find any good Getrag 265’s in Europe (commonly used in several BMW’s and Volvos), please drop me a line as he may be interested if the price / model year is right……..