The Wayback machine has stored a copy of the WRG 1925 to 1950 armor and infantry rules from 1973.
WRG
WRG Ancients 7th Edition
WGR Ancients 7th Edition is available for free as a pdf download.
Wargames Research Group Ancients – 5th Edition
Wargames Research Group has a page with lots of their older sets available, including the Fifth Edition Ancients, which were the standard for many years.