I'm using the Geo Brick Drive (with built-in amplifiers), not the Brick Controller. The page numbers I was referring to were from the October 13, 2011 version of the manual, and it looks like there was a new version of the manual on April 15 that moved the relevant section to pages 138-140, but the information seems to be the same.
The suggested configuration (page 138, formerly page 150) that I used for the analog input is:
M505->Y:$078105,8,16,S ; ADC Input value (ADC5A)
M605->Y:$07810D,8,16,S ; ADC Input value (ADC6A)
M705->Y:$078115,8,16,S ; ADC Input value (ADC7A)
M805->Y:$07811D,8,16,S ; ADC Input value (ADC8A)
I7106=$1FFFFF ; Servo IC1 ADC Strobe Word