Edge connector pinout is identical on MB and DK:https://www.mikesarcade.com/cgi-bin/spies.cgi?action=url&type=pinout&page=Nintendo_Classic.html
The power supply, if you look at the part number in the Mario Bros manual, is a PP-7B. Same as used in DK, Popeye and others.
In fact, if you look at the majority of the part number in the MB manual, they are DK, DK jr and Popeye part numbers. The TMAU part numbers are new for MB, but spot-checking those parts, they appear to also be identical, just with a new part number (like the 44-pin edge connector).
So, the big things to check for: Is it truly a DK cab, with a 4-way joystick and with the ability to rotate the monitor to vertical orientation? Other than that, sounds like you would need to be prepared to buy a DK 2-board set to swap in (usually around $200 - $250, from any number of sources).