yes to all you mentioned.
I own my 2nd of 2 440 Darts. i've owned 3 Darts total. One 68 adn two 69's. There is nothing to it. Headers are easier on a BB than on a Sb in an A body. There isn't a crazy weight difference when it's all said and done. Less than 100lbs if you are looking at a 360
One thing that wil not fit that you didn't mention is the driveshaft. It has to be cut. (About 100-150$) at your local machine shop)
Schumacher makes the headers and the mounts you will need.
Engine Weights for reference.
Mopar 273-340 "A" V8 525Lbs
Mopar 360 "A" 550Lbs
Mopar 400B V8 620