Eileen,

Most of the information that I have found pertaining to the 3rd Georgia Reserves does not mention specific companies.
I've only looked at about 6 pension applications, none of those happened to be from soldiers who served in Companies A or B. Im almost certain that Joe Bledsoe, whose pension application stated that he was wounded at the Battle of Columbus which resulted in the amputation of his leg, was in Company D. I've seen other pension applications from members of Company F that document they were at the Battle of Columbus. In bound volumes of letters and bound volumes of transcripts published by the UDC at the State of Georgia Archives I found companies G,F,and I mentioned regarding the engagements in South Carolina.
The pension applications on file at the state archives will probably be the best resource for specific info on Companies A abd B.
Does the list of casualities for Coosawhatchie Station that you posted list the Regiments and Companies? I couldn't get the websites that you listed on your posting to come up. I am looking forward to reading them.
Hope this helps
Doug