Charles, step rate for conventional?
The 177th may be changing, but If they are changing frequencies, I'm surprised it isn't to a digital trunked system.
My experience with AF units (20 years active duty) using conventional channels has shown that they may be spread all over the band. I've seen command posts typically in the 148 range, security in the 163 and/or 173 range, fire almost universally 173 range, CE in the 148 and 163 range, maintenance in the 148, 163 and 173 range.
Most have an increment of 12.5 khz.