Wow, old old thread
Yeah I have a td07-8 and a td07-9 as well as a t78. The tdo7's use a cast downpipe with a pressure seal of sorts. I'm not sure what to call it. It's a ring that fits in a groove around the pipe and as you slide the pipe in the turbine outlet it compresses which in turn seals. It was fortunate that mine came with one.
Email me at morganf1@charter.net and I'll send you pics if you wish.

 

Oh, and for the record my t78 is larger than the td07's in almost every way. Wheels and housings both. They are not the same thing.