Copies of the manual can be obtained by LATEX-ing the file
SPECX_V6-3.tex in the [SPECX.DOC] directory. This includes
several postscript files; you may need to modify the \special
commands in the .tex file to make sure your DVI converter picks
these up correctly.
The index is generated using IdxTEX -- if you end up using a different paper size then the page references may change, and you will want to run this again before the final run of LATEX.