I retired in 2005 my health plan ended March 1, 2011 I am not eligible for Medicare until August 2011 am I eligible for COBRA for 5 months?

You should be able to extend with COBRA, depending on who you worked for.
COBRA can last 1 day or up to 36 months.

Did you work for a church or religious non profit? School District or government?
And what size is your employer? Lastly, what state are you in?

>Did you work for a church or religious non profit?

No a local HVAC company.
> School District or government? see above

>And what size is your employer? about 130

Lastly, what state are you in?

California

So you should qualify for COBRA, not Cal-Cobra for the next 5 months.