Hey I make ATI HD 4350 for Lion and Snow Leopard!
Steps:
1-Go /System/Library/Extensions and delete ATI4600Controller.kext.(If you have RadeonHD,ATY_Init,NVEnabler etc. delete them)
2-Drag your downloaded RadeonHD and 4600Controller kexts in Kextutility and wait for complete.
3-Open OS x86 Tools (or download and open).Press enable/disable Quartz GL And press enable.Wait for it.(Download From:http://code.google.com/p/osx86tools/...ls_1.0.150.zip)
4-Select Repair Permissions on os x86 tools and press run selected tasks.Wait long...
5-When finished, close the osx86 tools.
6-Open /Extra folder.
7-Edit org.chameleon.boot.plist
add this strings:

<key>AtiConfig</key>
<string>Motmot</string>
<key>GraphicsEnabler</key>
<string>Yes</string>
<key>PCIRootUID</key>
<string>1</string>
<key>UseAtiROM</key>
<string>Yes</string>
and save.

8-Go /Library/Preferences/SystemConfiguration and edit com.apple.boot.plist
add this strings:
<key>GraphicsEnabler</key>
<string>Yes</string>
<key>PCIRootUID</key>
<string>1</string>
save and exit.
Press top Apple Menu,select Reboot.

If you get Kernel Panics,Blank or White Screens:
Don't worry.You can fix it.
open your mac with -x
go /S/L/E , delete ATI4600Controller and RadeonHD kexts.
and delete added strings in chameleon.plist and apple.plist.

Sorry for my bad English