Parts needed to convert 1570 w/date to GMT:
#8038 - center second pinion 5.70mm
#8037 - Cannon Pinion 3.39mm
#8039 - hour wheel with double toothing 2.44mm
#8040 - 24hr wheel 1.41mm
#8035 - Calendar Wheel nut
#8036 - Date Jumper
#8006 - Yoke for cam
#8008 - spring for cam yoke
#8011 - stud for cam
#8030 - Center wheel with Cannon Pinion
#8034 - Calendar Wheel
8034, 8035, and 8011 are in a grouping on the Rolex sheets.
You can also find all the GMT parts on a parts list for the 1565GMT. GMT parts are the same for 1565GMT and 1575GMT movements.
The calendar ring (spacer) must also be changed. There is more than one p/n for them...7956, 8037.
Center second pinion #8038 is not necessary if you can find a sweep second hand with a long tube.
https://rwg.cc/topic/114671-rolex-1575-gmt-movement-questions
https://rwg.cc/topic/141303-cal-1570-gmt-tell-me-if-i-m-wrong/
https://www.ebay.com/sch/i.html?_nkw=rolex+1575+gmt+parts