Update: I have since turned this into a WinDbg extension.
Let us say that you for some reason have made a 64-bit dump of a 32-bit .NET process (possibly by mistake), and you need to investigate it. It used to be that you could just load it into the 32-bit version of WinDbg and use !wow64ext.sw to switch into the 32-bit view of the process, and then SOS would work fine. However if you try this with .NET 4.5/4.5.1 then this is the result:
So… what can one do then? Attempting to remove some checks from windbg and sos perhaps?
It turns out that this is possible. The following instructions works with windbg from debugging tools for Windows 8.1 and Windows 10.