What most links don't show is what party they were in. I did some research and found:
MEMBERS OF THE UNITED STATES SENATE
Walter F. George – Democrat – Guy who actually read the Manifesto into the record.
Richard B. Russell, Democrat
John Stennis, Democrat
Sam J. Elvin, Jr., Then-Democrat
Strom Thurmond, Democrat
Harry F. Byrd, Democrat
Willis Robertson, Democrat
John L. McClellan, Democrat
Allen J. Ellender, Democrat
Russell B. Long, Democrat
Lister Hill, Democrat
James O. Eastland, Democrat
W. Kerr Scott, Democrat
John Sparkman, Democrat
Olin D. Johnston, Democrat
Marion Price Daniel, Democrat
J.William Fulbright, Democrat
George A. Smathers Democrat
Spessard Lindsay Holland.Democrat