8 3/4 axle vent bolt

Are there differences in the size of the vent bolts for an 8 3/4? I took the one off my spare from a 65 B-body Wagon 741 case and it was too big for my 69 A-body 741. I know the pumpkin doesn't matter, it's the axle housing. Also the two had different splines. I do not know it the one in my Dart is OEM. It's not a matching numbers car. I'm pretty sure the one from my 65 wagon is original.