Well this escalated haha. Few things in response:
1. Yes eBay sockets are crap and this was largely the cause of my problems however you can't wire the stock ones to fit as they only have two wires coming from them (unless of course you get Gen 3 loom but you wouldn't mod as thats quad already).
2. Yep there is a loom around that gives you the quads, I think gen2 and upwards JDM had it and Gen3 upwards from Aus had it. Fun fact, the Aus quads have all 4 as brake lights but only the two outers as tail lights.
It's much easier to just buy $10 worth of gear and do what other have done than chase a harness down though.
3. The Gen1 loom that I have did have dual filament sockets, used so the lights would go super bright under braking, but they didn't utilise the low brightness feature of a dual filament globe.
4. If you're doing the mod never use stock sockets as they only have 2 wires (earth and positive) so you won't be able to make the circuit without extensive hacking and modification. It's much easier to use the crappy sockets but get the wires worked out before you start the procedure and use a multimeter to check there is resistance in the wires.
5. Of course the quads are legal in all states and territories that the MR2 was sold in. Like Dudeman said its brake lights test and then tail lights test and both passes.