I looked a bit around the different IARU region bandplans to find a suitable QRG for VarAC in the 80m band. Not that the recommendation frequency must be the same across the globe due to the behaviour of the band but it could well be.
Looks like the range 3605-3620kHz would be available worldwide for 2700Hz wide digital mode transmissions. Regions 1 and 2 already from 3600kHz, whilst R3 has emergency center frequency at 3600kHz with +-5kHz span
Are there any frequencies already used as 'standard'?