I have a client with a SIMPLE 401(k) Plan. They would like to start a safe harbor 401(k) plan next year. I know one of the requirements for sponsoring a SIMPLE plan is that the "eligible employer" can not maintain any other plan which means my client will no longer be an employer eligible to sponsor a SIMPLE 401(k) Plan after it commences its safe harbor 401(k) plan in 2011.
Is there any way to convert a SIMPLE 401(k) plan into a safe harbor 401(k) plan or merge the SIMPLE plan into the safe harbor 401(k) plan or must the client terminate the SIMPLE Plan? My client would like to avoid triggering distributions under the SIMPLE 401(k) Plan. Is there another way to accomplish this besides merging or converting?
Any advice is appreciated.

I'm pretty sure you can just amend the existing plan into a "regular" 401(k). For the reasons you mention, it should be effective 1/1. As I understand it, a Simple 401(k) is just a qualified plan with special provisions, so there's no reason not to be able to amend it...that I know of.