440 Big Block in my 1970 Dart

1. Yes
2. Not necessarily although the earlier stuff is generally preferred for performance/durability.
3. Lots to change.You'll want to consider brake and suspension upgrades too. (see below)
4. Depends

Schumacher will have what you need to do the swap and a lot of your questions can be answered at their site: www.engine-swaps.com

bigblockdart.com is dedicated to BB a-bodies.