I'm going to sticky this cause I know its a topic that always causes confusion. While the 2g accord ran from 82 to 85 there were some major changes made for the 84 model year which means some some of the information talked about in here will be specific to either the earlier or later modles. Most of the mods, esp. the engine swaps pertain to the later. The early 2g accords had an EK series engine. This was a 1.8l 8 valve cvcc engine in the same family as the old cvcc civic engines. There really isn't much you can do with the early cars as far as drop in motor swaps. The EK in the car is the largest highest output motor that honda made that will mount with out any modifications. The answers to any swap questions on these cars will be custom. In 84 the accord got the new BS series motor. This was a 1.8l 12 valve cvcc engine, the same motor that went into the 84 prelude only with out the dual carbs. These motors were the begining of the family that would include the a18 and a20 engines found in the later 2g preludes and 3g accords making swaps very easy.
What is the same between the 82-83 and the 84-85? After reading this it doesn't seem to be much, but there are some similarities. The electrical systems of the 2 cars is very close. Each year more and more emission controls were added but over all the layout and most of the electrical components were the same. The suspension is also similar. There are a few diferences with the front subframes to accomodate the diferent motor (and no, the sub frames do not swap between modles) but other then that they are quite similar. Steering, breaks, etc.
Remeber when you post make sure it is clear which year you are talking about or you might get some bad information.