Anyone swap a Tremec T45 in their 67-69 Dart?

Gear Vendors? I've never heard of it. Is it like a stick?
No its an add on gear box that I think is controlled by switches. If you want to bang gears you'll need a manual trans.

https://gearvendors.com/index.html
Anything short of stock 4 speed will require a larger tunnel unless you go with American Powertrain and even then there is surgery. Stock will still need the hump installed.