This isn't exactly "non-PC engines", but can one easily run older engines via an emulator? I used KEGS (Apple IIgs) a few years back for some other stuff, which would be a 2.8MHz 65816 I think (the emulator can reach much higher speeds).
A flip-side of this could be to slow down engines for modern computers by running them in a virtual machine (such as valgrind, so that go wtime 1000 would only reach a small depth.
