Warning: the Cyberbass practice files include the soloists. Choir part is near the end.
http://www.cyberbass.com/Major_Works/Mozart_W_A/mozart_KV626_requiem.htm
In this recording, the soloists sing for the first 3.5 minutes. Choir entrance is at 3:55. Drag the slider to about 3:55. (In the score, the choir entrance is on the last page.)
St. Louis Church Choir 