here's the 5-inch exhaust flex coupler welded into my front pipe.
Been there a year, no cracks so far. This was welded by an exhaust shop in orlando, I installed the APN header and he did the rest.
One of my commercial accounts (I work at O'Reillys auto) keeps them in stock. I went to Ripley muffler right down the street from me. It was about 80.00 for the whole job which included the parts and labor. plus they welded up the rest of the exhaust for me aswell.
Oh, I'd figured any shop could put them in - I just wanted to make sure that just about any shop would have them to put in from the off...
Once I get the engine management done on my 88 (right after I get that 1990 cut up, and we'll probably move again in the meantime. Damn...) I plan to redo the exhaust as well - and I've been thinking about sticking in a flex coupler there anyhow.