Converting a two unit condo into a legal duplex

[Bryant Mortimer]

I am hoping someone has experience or insight into converting a two unit condo building to a legal duplex. I am familiar with the duplex to condo conversion but I am having a hard time finding any information the other way. 

A little background on the property, it was originally a rowhome that was converted into a two unit condo building. I purchased one unit in 2016 and then the second unit in 2021. I am getting ready to move out of the building entirely and would like to disband the condo association and have one tax id for the building as a whole. I am not 100% certain of/if there is any tax benefit(s) but given my plan to hold forever it seems like having everything under one umbrella makes the most sense in the long term. Any advice/thoughts/opinions are more than welcome. Thank you!