I would put a PPC card into a 68K only if absolutely needed. I have a Daystar 601-100 in one of my 950s because the AVID system needed PPC and 4 Nubus slots to work leaving me few options.

I also have a Quadra PDS 601-66 sitting around.

The faster 68k's would run 68k code faster then a 601 would in emulation, most PPC code would run better on a 604+ CPU. There is realy little need for a slow 601 in a 68k Mac.