No, it's not possible.

The holes are in the wrong place, the mk1 has components heatsinked to the back panel (hence not enough room to fit it), different internal connectors, etc etc.

It'd be an easier task to replace the 16-way red range connector on the back of the mk1 with a 24-way one. This is a huge beast, but it's the same height, so you'd just have to widen the slot. If you're having problems with the connector, we have some spare internal harnesses (and maybe 1 or 2 spare external ones returned under warranty which could be checked & fixed) for the mk1. Ask Rob, we might be able to get something sent off to you.

Hugo