He should easily qualify for SSDI. Contact the local SS office for an appointment. You MUST bring in copies of his medical records and Dx reports. There is a 5 month eligibility period which is retroactive to the date of disability (they start paying one month later). After 2 years he will automatically have Medicare as well. he will need a certified copy of his birth certificate also when you go to the SS office.

It only took me a couple of weeks to have my claim approved. It was based mainly on cancer fatigue.

Of course I am not sure about the post office thing. Some gov't employees are members of PERS (Public Employees Retirement System)or other retirement systems and don't pay into SSI so he may not be eligible. You'll need to find out whether he has been paying into social security. Check this out:

http://www.postalworkersonline.com/benefits.htm