EDIT Oct 17,2015-- There are 4 different keys, not 2. While they look the same, HD72 and HD73 key blanks are used for 75 and 76 OEM locks. HD74 and HD75 are used on 77-79 GL1000's, 80-83 Gl1100's, 84-87 GL1200's, 88-00 GL1500's and many other Honda motorcycles. 83-00 use different codes making some of the wafers different that won't work with keys from the other codes. If your locks use the same codes (5 number, 3 number, 3digit alpha numeric) and have the same profile, you should have no problem re-keying them the same.
On a side note, the later keys (HD74 and HD75) will usually fit and work in the earlier locks (HD72 and HD73.) The reverse is NOT true though. HD72 and HD73 keys WILL NOT insert in locks built for HD74 and HD75 keys. Also note that the key numbers I'm using, HD72-75, are Ilco EZ numbers and other key blank manufacturers may or may not use these numbers.

Keep in mind that rekeying a lock will make the key code on that lock invalid. You probably should obliterate it to prevent future confusion. I have a keying kit for Honda cars that the wafers work nicely in the Goldwing locks.

Starting at the end first the actually rekeying is fairly easy. I am starting with this first because the procedure is the same regardless of the lock being rekeyed. Disassembly for the different locks follows the rekeying procedures.
REKEYING THE TUMBLER
Insert your key and see how many wafers are already lined up flush with the edge. Remove the key and the wafers that didn't line up. Try the removed wafers in different positions until as many as possible are flush with the edge of the tumbler with the key inserted. In this case I got 3 to line up.


At this point there are several options.
1. Leave the wafers out but be sure to remove their associated springs so they don't fall out and jam the lock.
2. Replace the wafers with the correct ones from a wafer kit or a donor lock, if either is available.
3. File the mismatched wafers down until they are flush.
I have used all 3 methods over the years, and they all will work.
Remember to always exercise the lock with the key after reassembly and installation and before actually locking something.
DISSASSEMBLY INSTRUCTIONS
GL1100 SADDLEBAG AND TRUNK LOCKS



Remove the circlip from the back of the lock and the tumbler will come out the front. Watch the orientation of the parts so they can be reassembled correctly. Put together wrong the lock won't operate properly, if at all.
HELMET LOCK
Remove the screw holding the cover on the back of the lock. (Some of the locks have bradded posts holding the cover on. I have had success by prying the cover off the posts. The cover gets bent and must be straightened out to reassemble. When the lock is mounted, the cover has nowhere to go, so I don't worry with reattaching them.)

Remove the cover while pressing in on the helmet post. The post is spring loaded and will fly across the room if not held in place.

There is an extra wafer in the tumbler to lock the tumbler in the housing. Depress this wafer flush with the edge of the tumbler with a scribe or small screwdriver. While holding the locking wafer the tumbler will now come out the front of the lock.


Again make sure the parts are placed right when reassembling. Don't misplace the locking wafer or the tumbler won't stay in.

Again hold the helmet post all the way in while reassembling.
GL1100 TRUNK ATTACHMENT LOCKS
Remove the spring and strike. The small cam is held in position by the back of the tumbler, so the tumbler has to be removed with it in place. A circlip holds the tumbler in place and has to be rotated to a position so it can be pried out. The tumbler then comes out the front of the lock.



Once again watch the orientation on reassembly for proper operation.
HONDALINE SUITCASE LUGGAGE ATTACHMENT LOCKS


Remove the bracket from the back of the lock. There are 2 rivet posts holding the innards in the lock. Break them loose and the guts of the lock will come out the back. Again when reassembled the bracket will keep anything from falling out so don't sweat the rivets.
75-77 SHELTER LOCK


Remove the circlip and the tumbler will come out the front of the lock.
I have been unsuccessful, so far, with the following locks.
1. Ignition (destroyed the lock in the attempt)

2. 78-79 Shelter lock (have 2 with no keys and need one now, so will probably be destroying one soon)

3. GL1100 Shelter locks (was able to do, but required prying the chrome ring off the front of the lock and I was not real happy with the cosmetic result. But the lock DID work)
So on 78 and newer try to have matched locks for the ignition and shelter cover. All the rest can be easily keyed alike.