A 6mm (or 8, not sure) flat plate appropriately shaped will fit R31 discs and calipers. Bolt the plate to the inside of the end flange using 2 longer bolts. Think I have a template floating about somewhere.
Cheers.

If your axles are the same length you could try swapping left to right? I just did this on mine that's sitting on the floor and it moves the calipers to the back just above the spring perch.

The downside is having to work something new out for the handbrake cable which is now sitting in a funny spot. Might make what you have workable though.

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that is a great idea i hadn't worked out, but the same problem as if i flip the backing plates 180... that handbrake cable...hmmm

i wonder how hard it would be to adapt some flexible handbrake lines to work with that (which is essentially what the r31 brakes gives me)... might have to head to pick a part and see how they hook up

I was looking at it thinking some pulleys attached to the right spots might do the job. I reckon you can figure something out for the handbrake.

I'll try find a pic of my set up.
I've got limited time online atm.

Here's a pic of the one my mate did. his thread shows both versions of the caliper plates.
http://www.nzdatsun.com/forums/viewtopic.php?f=9&t=15&start=10
Login maybe required to veiw, but it only takes a couple in mins to register.

I've had a couple of ideas about the hand brake. One is to weld another arm on the other side of the leaver and set the cable up to pull it toward the aluminium backing plate. I see this working by using a cased cable with the free end fixed to the backing plate. With enough free lengh the casing should pull toward the backing plate. SO far that's the simplest idea I've had.

Something else I'm wondering is if there's any other calipers that would fit that have the handbrake mechanism built in, like these:

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By my measurement the bolt spacing on the rear calipers is 97mm.

As a side note, the caliper slide seals off the VT rear calipers I have fit onto the bluebird calipers. Good news since the bluebird slide seals are shot. Apparently PBR and Girlock share this part.

U13 bluey have an intergrated handbrake lever.