A user of MacEfiRom released a couple of tools for macs:

1) Upgrade utility to upgrade imac4,1 firmware to imac5,1, this allows you to upgrade imac4,1 with core2duo cpu and install more than 2GB memory, so you can install and use Lion on it
2) Upgrade utility to upgrade 2006 MacPro1,1 with firmware of MacPro2,1, this brings support for some CPUs to MP1,1
3) Tutorial for installing Chameleon on a Mac, so you can boot 64-bit kernel on a Mac with 32-bit efi and 64-bit cpu.