The Uniden Bearcat 278CLT uses an MC3361 receiver IC. This IC is located on the bottom on the main circuit board. It's quite an operation to reach this IC: 8 screws have to be removed before the main PCB can be separated from the bottom of the scanner. However, the unfiltered baseband audio can easily be taken from test point LND8.

(U)BC278CLT

LND8 contains the baseband signal.
A ground point is close

The connection to LND8 and G

Overview of the discriminator output

The chassis terminal is mounted above the external speaker output