Here are some comparisons of the assembled 1860 Army Colt grip on the Ruger New Model Blackhawk as compared to a pristine and bone stock 1968 Ruger Old Model 3 Screw Blackhawk. (Comparisons to the 3 screw are made cause I don't have wood for the New Model frame....just an ugly Pacmeyer and I don't want my old model wood buggered by movin it around on frames. But, the comparison's below to the Old Model frame should be close enough to the New Model to give one an ider of the changes.)
The 1860 Army Colt grip has a lot less wood down the back than the Old Model, effectively allowing smaller hands to reach the trigger.
The 1860 Army Colt grip has a lot less wood all the way around than the Old Model. It'll be more pinkie wrap friendly for everybody.
The 1860 Army Colt grip is lots longer than the Old Model.
From above you can see the 1860 Army Colt grip is smaller and slightly more forward than the Old Model.
With the faces of the recoil shields lined up we can see some differences in the thickness and length of the trigger guard loop and plate where it attaches to the frame.