If you have invested in that much OM glass, then I would definitely advise you to get your hands on an OM2n. I've owned, OM1, OM1n, OM2, OM2n, OM2 SP, and an OM4 in my time and, for what it's worth, I believe that the OM2n is probably one of the best film SLRs ever made.
The metering (with or without flash) has seldom been bettered and they are simplicity itself to use - once you've mastered the placement of the shutter speed dial which, once you do get used to it, turns out to be in a very good place indeed.
By all means use the lenses on your 5D but, if you have the chance, have a go with an OM2n and see what all the raving was about in the mid-late 1970's....