Pretty sure you will need - Gearbox, driveshafts, hubs, gear linkages and cables. IIRC the front cross member may require alteration as the Getrag box is wider than your MTX75. Pretty sure you need to replace the clutch aswell!

You'd be better off sticking with your current box which is more than capable of holding the power!

A ST manifold should see a reasonable hike in power but not enough to warrant a new gearbox

Rich