As per Chuck... We need to remove the old serial number and applied the original.
Contacted Lycoming to verify the proper procedure to keep the paperwork in order. They verified that the case serial number needs to match the original data plate. Lycoming also mentioned sense we upgraded to a wide deck the data plate will have to be stamped with the -36A designating it is a "Wide Deck"
I removed the serial number and stamped the correct number with the "A" designation as required. I will follow-up with a detailed write-up in the engine log.
