Short answer is you need an Archie auto adapter plate and supporting hardware.
The Archie adapter plates are different between the auto and manual kits. The auto is thicker and has a different starter mount method because the auto kits use a 142 tooth ring gear and the manuals use a 153 tooth ring gear.
The archie kit, for the auto, use's a engine to trans adapter, a crank to flex plate adapter, a archie flex plate, a starter mount that is not the same as the man trans kit. I did one of the 1st sbc to over drive auto swaps with his kit. I had him make me a custom drivers side axle so I could keep the v belt in side the frame rail. It was a lot of work. It was worth it.
