If you're wanting low end torque, go for the 347....no real reason to skip out on free cubic inches and power. All that you've heard about long stroke engines not revving or 347's using
oil are internet wives tales, perpetuated by people who don't know...
The aluminum block will not be noticeable in the car unless you're racing scales and you'll save about $4500 on the build. Aluminum block builds are noticeably higher on the build difficulty scale as you have to account for the block's expansion in bearing clearances, valve lash/preload, and deck height.