Did you ask the guy at the Truck Shop how much his conversion was? No free lunch when it comes to this stuff. Do some research and add it up: 700R4 transmission with a torque converter, flex plate, TVS cable, trans cooler & lines, rear cross member & mount, modified drive shaft with new slip yoke. Also shifter assembly. Labor to remove existing components & rear cross member, install new components & fluid.
It could very well cost over $3500.
Fred