Correct crystal to use for burning boot loader

I have some Atmega328P-AU that I already burned the normal UNO bootloader onto, but now I am going to burn the 8mhz, 3.3 volt bootloader on them. I'll be using a TQFP32 adapter. Should I set them up with a 16mhz or 8mhz crystal for the bootloading? Once finished, they'll run on 8mhz, but currently they run on 16mhz.