Hard to say for sure from the one picture, but that looks like a 66-up big block B and E body as well as 67-69 BB a body fork. If it is it should be 10 7/8" long. Early A body clutch fork are 10 1/2" long.
You don't say what year A body you have or the engine your running. If its a 68-up small block, I can say its not the correct clutch fork as its too short. Here is a link to brewers sight to help, and they have great information on there website.
http://www.brewersperformance.com/products.asp?cat=102Matt
