If you have the Pypes XFM16 or XFM36, then yes, they will fit the BBK shorties. Now the real question, why? The x-pipe, good idea. Shorty headers, not so much. They don't do crap for these cars. They don't flow really any better than stock manifolds, but they can save some weight. As for power, you might as well buy a Tornado Turbonator for real power gains!
In all seriousness....if you NEED new mainfolds, and these are an insane deal get them. The effort that will go into installing them, with the cost vs performance, it just isn't worth it. Save your money for a set of Long Tubes, then you are talking. The Pypes X-pipe will fit with the stock manifolds. I ran with stock manifolds and a Bassani x-pipe until my total engine rebuild. Then I put on LTs.