LarryD - now I understand what you are saying.
Drive High/Low on 74HC154 using Atmega pins 27 and 28 (Arduino A4 and A5)
This means I need to connect Jumpers JP1 and JP2 and disconnect Jumpers JP3 and JP4.
This will solve the intermingling of programming TTL pins 4 and 5 with Atmega output pins 2 and 3.
I wanted to connect a Real Time Clock DS3231 to Atmega pins 27 (SDA) and 28 (SCL).
I would think I would not be able to do that if using these pins for outputs to HC154.