Thank you all!
This has proven a little more challenging than I expected. Some prime candidates that I had in mind worked fine but on others I had to give up. Color selection without having visible edges was a huge headache, particularly where I wanted something significantly different than the default rendering. I did a little reading but I'm still not able to do it well enough that I had to abandon my hopes on some, at least for now. Even using Silver Effex didn't turn out helpful.
Another issue that I didn't expect (I guess not enough B&W photography in the old days) is that yellow and white render practically identical. Trying to get them to differentiate without breaking the transitions was another headache.