No ideas? :(

C'mon, otherwise i'll use papyrus.

I think the problem is that we don't know what it is you're going for: contrast, harmony? What's the piece for, what's the feeling?

I have a hard time understanding why you're using Letter Gothic for body copy (unless it's short), but perhaps Franklin Gothic for titles? .... unless you're looking for contrast, in which case you the field is wide open. You could go with a fifties script, for example.

You might look at something like Unit, which has a broad range of weights, and could be used instead of Letter Gothic, and might be an improvement, IMHO.

I have a cookbook, text is set in Meta, headlines, subheads and display set in Letter Gothic, which looks quite good. For your project you might look at Meta Condensed ... or as John Nolan mentioned – Unit.