Perfect partner for Franklin Gothic?



Currently doing some editorial design work and selecting two typefaces, a serif and sans, for the project.

I've settled on Franklin Gothic for the first type family due to legibility, style and weight variations, but for extra flavour and for body copy in feature articles, I'm looking for a serif that matches the same kind of x-height and will harmonise nicely. I thought of Caslon but think perhaps the x-height is too small; Palatino compares in scale however I'm not too sure about the combination of style - any thoughts on these or any serifs that may play happily with Franklin?