You have the same device id as me so no need to add anything to the kexts.
Try using chameleon wizard and set SMBIOS to macmini4,1 or imac12,2
I remember booting to a black screen when I changed that to MacPro.
I am not using ML atm as my 7750 does not work properly without the 10.8.3 so now i have got an extra GFX the GT210 which I want to make it work in Lion 10.7.4, I got it working in SL but now again SL is mis-behaving.
So I need to enable the GT210 in Lion . I changed it to iMac 12.2 but no qe/ci or resolution change. I am going to be reinstalling Lion tomorrow as its 1 a.m. here.