Is a CFI needed for check ride?

In the process of purchasing a 415C. I have a pilot's license but have been inactive for many years. Lately I have been doing re-training with a local CFI in a Cessna. The question is, do I need to have a check ride in my new 415C with a CFI who has flown Ercoupes? The gentleman selling the plane has had it for 8 years and flies under LSA but he also has a full private license. He has said he will give me as much dual instruction as I need or want. So the question is, do I need a CFI to go with me in the Ercoupe and must that person have Ercoupe experience and does it matter if I fly under LSA or 3rd class private pilot rules as it pertains to the need of a CFI check ride? Thanks in advance for helping me clear up this confusion.