Or you could do what many hotroders do, use the corrugated flex stainless tubes. Usually they use hose clamps with special rubber couplers to hook them up. I'm sure you've seen them.
I did it a little differently. I was using 1.5" tubing to hook up my 4.6L DHOC conversion. I used (2" OD I'm pretty sure) flex tubing tack welded and then silver soldered to make the seal to lengths of 1.5" strait stainless. If you cut the flex tube in the middle of the rib it leaves a sort of U shaped ring which the 1.5" tube buts up to. The picture shows the end result.