It should be easy enough to remove the packers, especially if the U-bolts are already loose. I would jack the car up and support it on the chassis somewhere near the rear engine mounts. If the U-bolts are taken out the whole axle assembly will drop down until it is resting on the ground on its wheels. I can see no reason for having the packers. I would put some grease on the aluminium spacer to deter corrosion. In your photo the u-bolts appear to be incorrectly seated at an angle, this will also loosen them as they try to straighten. When refitting the u-bolts get them vertical and paralell to each other before doing up the nuts. This should improve the handling of your Ruby a great deal.
I have not heard of packers above and below the aluminium block on imported cars. I would leave them out.
The fact that the front spring has a slightly curved top does not seem to affect the local Australian cars if they are fitted without any 'soft' packing.
I have removed the packers using the procedure suggested by Malcom and it was quite easy. The soft packers are of a material called hardboard in NZ. It is a dark brown material comprised of wood fibre and glue. It is often found as a cheap backing for wooden cabinets and chests of drawers. The packers were roughly cut and didn't match up with the full length of the aluminum packers. So I have thrown them away and reassembled using only the aluminum.packer. Time will tell if there was an important reason for the soft packers.
In my pragmatic approach I would have removed the hardboard, used 8mm spring washers and a dab of loctite in place of tab washers, bolted it up and driven away
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