To Buns1 (Electrical)
From QSE (Structural)
The latest ASCE Manual in circulation is ASCE-10-97. As MikeDB suggested, the commitee is working on a revision that will probably be available to the public within a year. However, do not expect drastic changes from the new Manual.
In any case the design/analysis/detailing/installation of Communication antenna supports on existing Transmission Line towers are NOT covered in the manual.
A word of caution: Transmission line structures are normally designed to their limits, that is why we do full scale testing on these structures, to ensure their ultimate strength. Adding antennas, particularly running several cables the full height of the tower require careful consideration. I do not see how Manual 72 can help you based on what you have described.
Suggestion: Get help from a Professional Engineer who knows Transmission Line towers.