First let me clarify something; all 63 Valiants are hot rods. It came standard from the factory, it's a one-year-only thing.
You'll probably get a sh1t storm, but I see nothing wrong with crossbred hot rods. Plus that AMC V8 has the distributor up front and will save you a little firewall surgery. Of course your pushbutton 904 won't bolt to the back of the AMC block, but if you have someone that can do some machining you could build an adapter or make the necessary changes to the AMC case. FWIW, I had a 65 Cuda that had a floor shifted 904 that used the duel cables and I made it work.
In any case, it'll be yours and unique when you're done.