I hope that this doesn't sound too stupid, but I bought the mounts from J.H. Whitney a few years ago and forgot the numbers for the order. You see I had ordered them a while before finally installing them maybe 2 years ago.
I am not certain of the order numbers since they are possibly from a 1997 catalog.
I had the transmission rebuilt in 2000 and that is when I found the mount in my shop where I had stored them. I had heard of these poly mounts from 4x4 Wheel Magazine in an article from 1998.
I do like the mount it seems to keep the engine pretty consistantly stable. There was possibly some overkill in a poly mount for the transmission case so maybe a new rubber mount will do as well. There is usually not much torqueing around the case mount, and so it will usually last the length of the vehicle.