I agree with Craig on running sidepipes.
I've been building my own headers and sidepipes. I picked up a DIY header kit from DiFilippo that has the laser cut header flenges, gaskets, collectors and a ton of 90 and 45 degree mandrel bends. The whole kit was about $385 and I'm having lots of fun building them. There are a bunch of pics in my gallery that might give you some ideas.
I'm trying to write an article for the next snake tales on DIY headers that may help too.
As to sidepipes being illegal in Victoria... The problem isn't the sidepipe as such it's the fact that the exhaust exits towards the pavement. I spoke to my engineer on this and providing they have cat converters, duct the exhaust to an appropriate location and have adequate protective shielding on the pipes you will get through (I plan too). And if the shielding and the ducted exhaust just happen to fall off after it's registered, I'll just have to live with it I guess
I didn't want to build a complete rego exhaust only to replace it with the sidepipes afterwards so I set about building a system that will comply for rego and that I can quickly/easily change to the configuration I wanted after rego with minimal changes.
Cheers