Yeah, the pictured one doesn't have the same exhaust manifold flange. But it sure would be nice if someone made a nice, long runner header like that. *coughMAMcough*
Anyhow, the flex section isn't designed so it gives you more wiggle room... You actually want to load up the flex section as little as you can, because that will be the weak spot in the exhaust, but should be enough to dampen the motion of the engine, as transferred through the header and midpipe. These can be purchased locally, but I purchased mine through the same company who I purchased the tubing and flanges through, so I could make sure it was all stainless steel, rather than stainless with mild steel bits of hardware in there.
You have to be careful while lining these things up. Just cut the pipe properly, first, then, while the pipe is held in place, tack weld the flange in two places. Line up the rear flange, and tack weld that one in two places, too. Do this with each piece of the puzzle; The flange, pipe, flex pipe, cat, rear pipe, and rear flange After that, I went over to my friend's father's place and used his TIG welder with some stainless rods, and practiced for a while, after which I welded it up fully, and have had no problems with it since.
Just take your time, and be careful. Also, MIG should work fine for your exhaust all the way, but I TIGed mine, just because I wanted to learn how to do it, basically.
