Convert the image to a Master Boot Record format: hdiutil convert /path/to/filename.dmg -format UDTO -o /path/to/output.cdr
Where to get installers:
Apple transitioned to 64-bit processing in phases, changing how the operating system interacted with Intel hardware. mac os x iso download 64 bit top
You can download installers for various 64-bit versions through Apple's official channels: Convert the image to a Master Boot Record
Create bootable USB (Intel):