Warning: I found an error if the DR position is on the southern hemisphere. The PUB249 pdf files did not show this error and are correct (as far as I checked). All Revisions 8+ and the Windows release have been fixed.
This Python TK application calculates a good set of stars for a 3 star fix, makes all calculations similar to the FAAs Celestial Computation Sheet (see FAA doc FAA-H-8083-18).
Also, you can create a PDF file that generates Pub 249 Vol 1 for any epoch you specify.
The PUB249...