I think i did a write up on this before but I am going to start a new cleaner how to on this here.
Unlike the 3g its very easy to swap rear disks on to a 2g. 2g's never came with rear disks, even the SEi had drums, but the rear suspension is almost the same as a 2g prelude and the breaks will bolt right on.
A very tiny bit of welding is required for this. I mean very tiny as in you will have to have about an inch extension welded on to the threaded rod of you e-brake handle. Just about any shop with a welder can do this (think exhaust shop) and they may not even charge you.
You can source all the parts you will need from any 2g prelude with rear disks. I beleve some ealry 84s didn't have disks but the rest did. They are usually fairly easy to find a self-serve junkyard.
You will need:
All of the parts from the rear spindels of the prelude. (I'll explain later)
The prelude rear calipers and hoses.
The e-brake cables.
And the proportioning valve.
To get the rear spindle parts:
Remove the caliper.
Remove the carrier bracket.
Remove the brake rotor. (The rotor and hub are one unit, pull off the center dustcap and remove the nut to remove it. Remeber the nut on one side is reverse thread.)
With the rotor out of the way you will see 4 bolts around the stub axle, remove them. The mounting plate that the caliper carrier bracket and the dust shield should come off, you'll need them and the 4 bolts (one can never have too many bolts).
The ebrake cables can be a pain in the butt because you have to get under there and remove the rear exhaust heat shields. If you like you can buy these parts new from the dealer.
All thats left is the proportioning valve. It's located on the front passengers fender. Just unbolt the lines and take it out. There is no need to make note what lines went where, its the same as on the 2g.
While at the junkyard its probalby a good idea to grab a spare e-brake handle. Its a good cheap source to get the piece of threaded rod you'll need to extend your ajuster.
Instalation is reverse of removal. The rear drums will come off the same way the disks did on the prelude and the prelude parts will just bolt on in their place.
The proportioning valve doesn't quite fit where the stock valve does. If you are a stickler for looks you could weld the prelude bracket on, or if you're like me you could just chop the stock on up and make it fit. The lines don't quite line up either, but you can adjust them easily enough. Just don't bend them too sharply or they will kink.
The harders part is the e-brake cables. The prelude's cables are about an inch shorter then the accords. The adjuster will just start to thread onto the accord handle, but it won't thread on securely. (I know from expierence, it will strip out and pop off, releasing you're e-brake when you least expect it).
What you need to do is get about another inch or so in length. The way i did i was to cut the full length of thread from my spare e-brake handle. Then I cut the thread on my e-brake handle in half and welded the rod from the other handle to it. I looked something like this:
X is the cut and W is the weldThe keeps the weld up away from where you need to thread the adjuster so you don't have to worry about grinding down the weld and threading it.Code:Spare handle: ===== X //////////////////////// My handle =====/////////// X ///////////// Weld =====///////////W////////////////////////
With that taken care of the ebrake cables will go on where the stock ones were. Some of the retaining tabs are a little diferent but you can pry the old ones off from the 2g cables and put them onto the prelude ones.  I've been told that some 2g's have the proper holes for the disk brake tabs, the holes are probably filled up with gunk and under coating. If your car has the proper holes then you don't have to bother swapping over the accord tabs. [/edit]
Thats basicaly it. If you get good deals at the junkyard it can be done for well under $100 and if you know your way around the car you can easliy do the swap in an afternoon.