32 and 64 bit installations on same medium?

ahoy all,

currently System Rescue CD provides a single downloadable image that includes both kernels for both 32 (x86) and 64 (x86-64) bit architectures

http://www.system-rescue-cd.org/Download/

while i am still trying to figure out how exactly this is done, is there any way to accomplish the same thing in Alpine? they use GRUB and i see what seems to be 2 kernels:

RESCUE32.
RESCUE64.

in the /ISOLINUX directory of the ISO image, so perhaps they are deciding during GRUB bootup what to do? while i realize that the configuration of GRUB for this setup is beyond the scope of this forum (though appreciated if you understand GRUB well), my main question is how to install Alpine to provide both 32 and 64 bit support on the same USB drive, SD card, etc?

thanks, w