yeah i have a tdo6 on my standard manifold, just had to put a spacer in there to get it to fit.. i have an external gate too. you need to get a pipe for the gate cast welded to run the external gate.. it is probably easier to get an aftermarket stainless manifold and moddify that.. i dunno depends whats available to you.
i am pritty sure the rb30 manifold is different as you pay $250 for them and about $50 for rb20/25.
sell the manifold on calaisturbo.com.au then buy a cheap ebay stainless manifold with an external gate pipe... you can get them for around $250 as well so you wont b loosing out..
you are going to have to do a bit to get it all to fit anyway. your dump/front pipe will probably need to be moddified as well as the intercooler pipes to get it all to fit and line up.