I wasn't able to get hold on a 360 gearbox in time so a crazy part of my brain told me that the input shafts would be the same on the 340 and 360 5 speeds. However, looking at the differences in the shaft lengths and spline pattern, the differences are quite apparent:
340

360

Ok, so I have 2 questions:
1) Can I swap over the input shafts? - I don't think this is an option as the front gearbox mount is going to be in the way of the 360 front plate.
2) Can I swap over the internals?