426 Wedge possible install challenges

I don't actually know what year trans is in it. My understanding is that the motor and trans that came with it were swapped there by a previous owner a long time ago and it originally was a 6 cyl. Might be the original trans. Not sure. I have to take it out anyway so I will figure it out at that point.
The trans will not work if from a slant 6.
V8 trans is different.