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Make sure you undo the hub nuts if you're going to refurb the driveshafts/uprights while they're still fitted on the car; it's a lot easier! The front nuts are an unusual size (29mm), the rear nuts can be 29 or 32mm depending on the car.
The whole rear section can be a PITA; the driveshafts can get properly stuck in the uprights and the lower wishbone to upright bolt is exposed, so removal a lot of the time can be problematic.
You'll most likely have an issue with the steering rack fouling the front lower wishbones at full lock and droop; there's lots of examples over in the States where the Miata has been a popular donor car for a lot longer than over here. There are several ways to fix it, which are covered on the forum.
You'll need a custom tank anyway, you can use the MX-5 sender and pump, you might need to modify it. Someone might even have a MX-5 tank for sale
Where in the world are you?