I'm looking for a short story that was published in Analog in the late 60s/early 70s. It deals with a group of scientists that are examining the remains of an alien craft that was shot up in space. They try to figure up which parts go where and what a series of enormous circuit buses do. Eventually they think the have discovered what seems to be a working FTL/hyperspace drive. The tests work and the drive is a success. Later they discover that the ship just had an ordinary drive and they made the wrong assumptions.
The short story “Dead End” by Mike Hodous was published in Analog in May 1967, ISFDb title, and deals with an attempt to give the aliens the chance to make the same mistake they did. Artwork for both stories was by Frank Kelly Freas, I believe.