A833 early gearset in OD case?

I too have a 833 standard 4 speed and its for e/b body. I not only want to make it for A body tail on it ( I have a bell housing for my slant already. Id like to know if I can make this a overdrive ? or should I just sell this entire thing and buy a 833od ready to go from brewers ? they are over 3k. And I have this amazing trans here already.