An intercom seems an overkill for a Pitts (unless it's an S2), but may help.
Most of the ANR headsets get swamped by a really noisy cockpit, so a passive arrangement might be preferable.
I'm a great fan of the intra-aural types and personally use the QT Halo with the yellow foam ear-buds. That outperforms my Bose in the RV.
I do agree with the recommendation of PS intercoms, though they don't control radio volume.
A cheap option that may work for you is to wear foam ear plugs under your headset/helmet and turn the volume up to compensate.