I realize this is nothing new, and I was hoping for no issues related to it. Aside from the fuel issue (basically my 996 cluster is about 1/8 tank optimistic) all is well. Gentleman I purchased it from pulled it out of his C2 when he did a full interior gut to turn it into a track car, I have not cross checked the part #, but have no reason to suspect it not being from a C2.
If the DME/custer re-set does not work, I will just have the dealer calibrate the fuel sender to the cluster and I have to think that should cure all issues.
Best I can tell from the 996 parts manual is that it is for a '02+ Carrera 2. The only numbers that didn't match up was the 76. The parts manual does list a 996 641 981 76 70C, but it lists it as a Carrera 2 / 4 / 4S.
By the way, I was able to get my cluster in on Sunday. The first cluster I tried was fried, but the second one works great (it's nice to have a backup). Mine's a tiptronic and the tiptronic readout works great. I did the OBC hack at the same time and the dot matrix display is very cool. I filled my tank prior to the swap and the new cluster read full when I put the power to it. I also did the litronic retrofit yesterday.