I created a version of Lion in WMWare first, this then allowed me to create a USB version of the unishit installer using Lion from the Appstore then installed on my i5 system.
Here is the site to create the USB version of UniBeat in case you don't have it.
http://tonycrapx86.blogspot.com/2011/10/unishit-install-mac-os-x-lion-using.html