Change Arduino Uno clock from 16MHz external to 1MHz internal
That will not work. To change the clock source, you'd need to change the fuses. I don't know of any way to do this while the chip is inside the UNO. 

Secondly, a factory fresh 328P won't work in an UNO board, because it doesn't have the correct fuses, and doesn't have the bootloader programmed. 

I'd suggest placing the 328P chips in a breadboard; connect the ISP pin to the UNO, and use the Arduino-as-ISP to change the fuses, and upload your program.

PS why run at 1Mhz. The internal oscillator runs at 8Mhz. By default the divide-by-8 fuse is set, so it runs at 1Mhz out of the factory, but you can unset this fuse.

PPS use this website http://www.engbedded.com/fusecalc/ to generate the right fuse settings for your project.