Final Drive options

So I'm looking to do a full rebuild on both my engine and gearbox and have decided I want to upgrade my final drive and maybe even go for close ratio gears.
I have looked around and the best I can find is the Gear X 4.06 final drive, does anyone know of them or can anyone suggest any other brands I could look at.
I'm going to be running a turbo'd B16a2 built engine at around 280bhp so want something to complement this giving me better acceleration and higher top speed.
Thanks in advance for all you help and advise.
I have looked around and the best I can find is the Gear X 4.06 final drive, does anyone know of them or can anyone suggest any other brands I could look at.
I'm going to be running a turbo'd B16a2 built engine at around 280bhp so want something to complement this giving me better acceleration and higher top speed.
Thanks in advance for all you help and advise.