If you goto the Flight Schedules site:
http://www.unitedcargo.com/utilities/cp1/frtSched.jsp
And search, you can see the different equipment types.
The downside is that it only shows results for the next 7 days.
47C is a new interior 747
747 is an old interior 747
A320 is mainline A320
20X is a TED A320 (not yet converted to mainline)
20Y is a TED A320 (not yet converted to mainline)
20D is a converted A320 (TED to mainline)
B757 is a 2 class 757
57P is a 3 class 757 (p.s. configuration)
I don't remember the code for the new interior 757... Can someone help?
67I is a new interior 767
B767 is an old interior B767 (now 2 class, since all 3 classes have been converted)
Currently there is no distinguishing between a 777 (2 class and 3 class)