.Net may or may not be an option here, not sure. The main dll has to stay MFC, performance concerns as well as concerns with how easy the code would be to disassemble. The part which does threading however is separate from that and converting it to .Net might work if there’s no way to get to using an I7 with MFC code.
I ain’t a C++ head, but if you have source, isn’t it nearly a nobrainer to compile to C#? I mean, yeah, pointers and garbage collection, but other than that?