I found a PDF copy but it is very clearly copyright to the author himself in 2004. I say this because copyright works differently for individuals and corporations. The copyright should last 70 years past the authors death, and may have been transferred to an heir or other party.
I'm not trying to tantalize anyone with the PDF... this is more of an informational post.
We know the copyright is 2004 and I've also found the inscription "Published by Datatec, Dallas, TX". However, I've not been able to find any information on the publisher at all so I don't know if copies can still be bought, or what the status of the publishing rights is.
It is 178 pages and there is what appears to be a home address and home phone # for McCombs. I haven't called it since I assume it would just put me in contact with someone with no relevant info.
Maybe someone here can do some better sleuthing on Datatec, or has more knowledge of copyright law.
Keep em' Flying
//Fight Corrosion!