let's see... original 3G was 834... replacement #1 was a 846....
replacements #2-#5 were 923's and my current one is a 926...
For 3G's I would be very careful with your 923's... the lot that my local apple store got of 923's were over 50% defective out of the box... and I'm not talking about small defects... some had plastic (molding) defects, some were DOA, some already had dust under the screen and others had clusters of dead/stuck pixels....
For 3GS's my brother has a 923 and it's perfect so far... it seems like they put some rookies on the 3G's that week haha