I really like how my '77 EB box drives, but am upgrading to a 4x4x2 box to run 37's with a hydraulic ram-assist for the beefier sector shaft. I have a '77 F150 as well and have always liked how that truck drove, so I agree with Mad that you can't really go wrong with either box, though both are getting harder to find.
I have yet to drive any of the aftermarket boxes currently on the market, so I can't comment on those.