Help-67 Mustang C6 driveshaft

Hi, I'm switching my 67 390 Mustang from 4 speed back to the original C6 automatic. I've gotten most of the parts that I will need but I was told that the driveshaft on an automatic is shorter than the 4 speed.
Can anyone confirm this info? Any other info you could provide on what parts will be different would be appreciated. thanks, Rich e-mail rchapman at mail dot com

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