Here is a list of DVD drives I'm using successfully in the 600 class thinkpads...
05K8971 (SR-8171-H @ 2x) worked fine without modification (#1,2)
05K9106 (SD-C2102 @ 2x) worked fine without modification
27L3873 (SD-C2302 @ 6x) worked fine without modification
27L4213 (SD-C2512 @ 8x) transplanted into 05K8873 caddy (#3)
27L4355 (GDR-8082N @ 8x) transplanted into 05K8873 caddy
My definition of success is me watching a movie on a DVD -- commercial or burned. For burned, I played +/- r. I also tried to read a data dvd +/- r. I think I would avoid the 05K8971. I can't justify the caddy-obotomy except to improve availability -- the 05K9106 and 27L3873 work fine. I did not see any advantage to the faster spinning rate.
Happy shopping!
Notes:
1) Had to flash to 079g before it would read anything except commercial DVDs. Found files and instructions at
http://www.mazochungo.net/SR-8171.htm -- his commandline did not work for me. Instead, I simply entered t at the DOS prompt to run the included bat file.
2) Would not read +r data dvd (burned by me)
3) Would not read -r data dvd (burned by me)