The alternator from burton power would be fine, its just expensive! You can pick up a new fiesta/puma alternator for around £60, and a 2nd hand item for around £25. If you are desperate, you can pick up a fiesta alternator off thehelf at loads of parts stores. Thats the only reason i used it, but the burton power item is a lot less work!

I dont know a lot about the mazda gearboxes, but i think they need different mounts again, so you would need to make 3 mounts, rather then 2. The MPS box has an LSD as standard, so would be a good box to use, but the diff wont fit the focus/mondeo duratec boxes, so maybe the driveshafts are a different size?? Also a different linkage, that is a lot harded to get hold of. Mondeo, focus, and fiesta gear linkages are common and cheap.

For a mk4, mk5, or puma conversion, i think the ST150 box is the easiest option as you can retain the top mount, and original driveshafts, but depending on what power/torque you want to run, and the weight of your car, and how much time and skill you had, youd have to make the decision on what box was best! The ST150 box is also lighter.

The MPS box pattern is the same as the duratec, the block is the same, other then an oil return, and the head is very similar, but the injectors are under the inlet manifold rather then above like the duratec. Its DISI, cant remember exactly what that stands for, but its something to do with direct injection into the cylinder rather then above the valves. So inlet, or injectors from the MPS wont fit the duratec.