Are you building a 318 Magnum or a 318 LA? The LA blocks don't have the Magnum mounting provisions.

There are solutions to handle the electronics for the transmission, but you're not going to like the price. Here is one option: http://www.e-transcontrol.com/dodge-transmission/

Holley also has an option, but it's built into their fuel injection controller.

I agree with the previous posts you're probably better off going with an RH instead of an RE, especially if you're going carb.