I am in the process of swapping a T56 into my automatic trans am. I got a transmission out of an 06 GTO (or so the guy told me). The input shaft was bent so we ordered one for an 06 gto. But the input shaft we removed from the GTO transmission is different than the one we bought (which was ordered for a GTO trasmission). They are the same length from the top of the gear set to the end of the shaft. However my 4th gear syncro cone is different. There are 4 notches cut into the teeth that slip onto the 4 tabs located on the 4th gear syncro cone. From what I have determined, the input shaft from my transmission appears to be the same style as the ssr and cts-v. I am not sure if only some of the GTO trannys got upgraded internals but the shaft I bought appears to be the same shaft that would work with the standard 4th gear internals of the fbody transmission. The input shaft from the transmission is 26 spline 29 tooth. The diameter of the shaft I bought is slightly larger than the one out of my transmission and is 26 spline 31 tooth. The part # off my old shaft reads T0225 8 1121. Any help is greatly appreciated. I can email pictures upon request.