I am hoping for some input here. I am rebuilding a c6 transmission and I had to get another case. The original fell off the jack and broke 3 ears off. Now I got another case and started to swap the parts and replace clutches, sprags, etc. I have discovered a few things different as I got deeper into the tranny. There is no boss for the detent spring and there is an extra port for the valve body where the vacuum module goes to. Am I screwed with the detent spring? It is column shift and the tranny bolted up to a 390. No ID tags on servo cover or on the pan.

 

The case with out the linkage detent in the case and the extra port for the modulator is a 69 and earlier case , the other one is a late case.

You will need the valve body to match the case, so your late valve body will not work on a early case.