bb or sb for my 72 dart swinger

Hey guys I'm new to the board and also the proud new owner of my first dart. I have built many of Chevy motors and tinkered very little with mopars. I was wondering what are the pros and cons for small block vs big block. 440's are a dime a dozen around my area, at first I was thinking about a 360 and making a stroker out of it but they are soo hard to find. Now I'm tempted to go with a 440 because they are easy to find. My wife bought my this car and I'm deployed right now so its my project gift waiting at home for me to get started. I only have a few more months over here and I get to come home and start. Any advice would be helpful.

Thanks
Michael