Dipstick issues

I have a '64 Barracuda that has a 318 in it. I was pretty sure that it had the original trans when we bought it 10 years ago. I am just finally getting back to the restoration and noticed the dipstick that came with it has the end cut off it. So I ordered a factory one from Year One and it didn't fit, too long. Then my Dad went to AZ and found one from another '64 Mopar. But had the same issue as the Year One dipstick, too long. Any ideas? Is it not the original trans? What is the easiest way to determine what trans is in it? Thanks in advance.