The Peggy board has some plated vias next to each Atmega pin. I can solder to those easily and connect to RTC.
That connects my RTC to Atmega pins 27 and 28 (SDA and SCL) (need to remove Jumper JP 1 and JP2)
I also need to connect a second set for the A0 and A1 High/Low signals to 74HC154 pins 22 and 23 replacing the SDA and SCL connections.
I could use Atmega pins 23 and 24 (ADC0 PC0 and ADC1 PC1) which Peggy board has going to two buttons. Could connect them to 74HC154 pins 22 and 23 and like you say connect to 74HC154 socket pins on back of board.
Are these two pins suitable?
Thanks so much for your help.