Here are all the original UHF DEA frequency allocations.
409.6250 MHz, N156 - Repeater, Possible F1
411.1750 MHz, N156 - Repeater, southern AL Gulf Coast area
4122.575 MHz, N156 - Simplex, heard in AR and MS
415.6000 MHz, N156 - Input to 406.6000 repeater
These have been heard in the Dallas/Ft. Worth area:
163.2000, N156 - Possible input to 172.7250 MHz
165.8875, N156 - Reported weak in the Houston area
170.5875, N156 - Heard in the Phoenix, AZ area
171.5875, N283 - Heard in the Houston, TX area, used by DEA air assets ("FLINT") calling "FLINT Base". Frequency possibly called "AIR" channel - also note the unusual NAC.
Confirmed use in the Chicago, IL area: