Welcome to the site and good luck with your project.
As for the questions, I don't know if you could piece a 426 together and have it work/last; for a whole lot less than the crate engines, unless you luckily stumble of something. 6 pack intakes for hemis' would likely be made out of unobtanium. Most all 426s' run 2-4bbls. A Dana diff narrowed appropriately would compliment the build and it's axles will take pretty much anything a street motor could throw at them. The US Cartool subframe connectors and torque box kit is, in my opinion, the best way to stiffen them up. I believe any engine Mopar made, can be put into the engine compartment with the right mounts. There's many here way more knowledgeable, so see what they say.
