Need to power Arduino Mega 2560 with 3.3V I found an LCD for my Arduino Mega 2560 that's parallel (I like that, I don't like SPI), but it works at 3.3V and isn't 5V tolerant. That's why I'd need to use level shifters, but that would use too much space and I'd like to power the microcontroller with 3.3V. But that would cause problems because the USART communication is set to be on 5V and that can't be changed.

Is there a way to power my Arduino at 3.3V? Is there an alternative Arduino for that?

Also, if there is, I'd need to have a 16MHz crystal on it. I know it's overclocking, but Gamebuino works at 16MHz on 3.3V and I would like to do the same.
Have you considered maybe using the Iteaduino MEGA2560?

The Iteaduino MEGA2560
uses the same ATmega2560 processor as the Arduino Mega 2560,
but is physically much smaller, the size of a Arduino UNO.
It has a switch to run the ATmega2560 at 3.3 V, so its I/O pins can be directly connected to 3.3 V modules.
It breaks out all the GPIO pins of the ATmega2560,
so it actually has more I/O on its connectors than the Arduino Mega 2560.

If I'm reading this right, the Iteaduino schematics and a typical Iteaduino features list
seems to say it already has a 16 MHz crystal.