Dr. L. Tabor is a medical doctor who advised Dale Gribble to donate his kidney to John Force, but actually wanted the kidney to go to 10-year-old Timmy Croston. He appears in the episode "Dale Be Not Proud."
In season 8, Dale went to a hospital with Hank, Bill, and Boomhauer to test their blood type as part of seeing if they could help John Force's sick health. When Dale had his finger pricked, he passed out from a seizure. During his unconsciousness, Dr. Tabor tested his kidney and saw that it was compatible for John Force, but unknown to Dale the kidney was actually compatible with a 10-year-old boy with kidney disease.
Dale agreed to do the surgery, and Hank was given power-of-attorney to act as Dale. After the kidney removal surgery was completed, Hank found out from Dr. Tabor about the real match for the kidney, and Dale finds out too. Dale tries to leave, but Tabor and other hospital employees hold him down and sedate him. Dale pretends to agree to giving the kidney, but before the kidney surgery for the dying boy can be carried out, Dale sneaks to a storage room and steals his kidney from a freezer. Tabor and Hank search the hospital for Dale and surround him, but Dale threatens to cut the kidney if they come closer. Tabor lets him run elsewhere, but Dale comes across the boy and agrees to give him the kidney for surgery.