They are not pre 75 legal to race so no real difference in the bikes from a racing point of view. Actually this is where the pre 78 rules suck as you cannot change the shock pickup points so you are left with the measly 4.5 inches of travel they have on the rear!
Still a great looking bike (75 or 76)
This is the one I have (76)
They are a great looking bike and the power delivery is much better than the light switch '73 and '74 Elsinores. They also have a stronger gearbox by way of bigger dogs on the gears. It's a shame Honda chose not to increase suspension travel and beef up the forks because it would of made the bike more competitive.
There are aftermarket swing arms that move the lower shock point back towards the rear wheel so longer shocks can be used without stuffing up steering geometry. I had an original DG arm on a '76 CR that I had and it had 15.5" length shocks that gave a whopping 6" of travel
I still have a '76 CR250 waiting to be restored one day.....