GingerNinja How much can the T5 box take? I've got an EB V8 box to swap in soon and I'm hoping it will hold up to 350-400whp (whatever that ends up being in torque).
Do places like Mal Wood have the technology to make them stronger?
The EB V8 box (IIRC with tapered input bearing) is rated for 330 lb ft /100,000 miles.
The best V8 boxes with needle roller inputs are rated 300 lb ft/ 100,000 miles.
The Commodore 6 boxes are rated at around 265 lb ft/ 100,000 miles.
Shot peening, heat treating, and nitriding the gears helps with strength. There's also a cluster reinforcement plate from 5speeds.com which is better than the factory fitting. A mod to the 3rd gear wheel to assist lubrication also helps these things live longer. As does setting the preload correctly, and doing transmission fluid changes at reasonable intervals.
Of course, you can spend big bux and go with custom made gear sets, but by then you'd be spending the same sort of money that would get you a brand new Magnum box.