beta bios problem

[motorule]

i have a gigabyte ga-ma790fx-dq6 motherboard which i bought it used from the internet to find later that it is an engineering revision ( 0.3 instead of 1.0,1.1,2.0 etc)
comparing it to the retail mb pictures i found that there is a little difference in the numbers on its capacitors near the processor socket
the bios which was on it seems to be a beta and instead of naming it like the retail f1 ,f2 ,f3 it is called d18
the motherboard boot only if flashed by the d18 and the last bios f7g which is a beta bios too
after flashing the f7g a strange thing happens to the speed of the ram and cpu for example the ram speed instead of being 200x4=800 it will be 192x4 so it should be 768 but it will be 772 and the cpu speed will be 2600 instead of 2700
so now i need to made a mix of those bios files to make a one which is suitable to the engineering mb and have the last bios options and agesa as the d18 doesn't support the 1066 ram and my athlon x2 7750 which is only supported by the last bios f7g
so i need somebody to explain the way to do so to me if possible
Any help will be appreciate and sorry for my bad language