Bill, once you achieve full retirement age, any Social Security Disability no longer exists and you receive retirement benefits.
Disability benefits are only available if you are less than full retirement age AND you are unable to work due to a disability.
If you voluntarily quit work, you will be denied disability benefits anyway. In order to qualify for disability, you would need to go through a lengthy process to verify your disability, and by the time that happens, you would have likely reached full retirement age, thereby making the process mostly moot.
If you were to receive a disability benefit, when you hit full retirement age, the amount would be the same as if you had not received a disability benefit, and as stated earlier, would be called "retirement" benefits even if you were disabled.