I do them both on a regular basis, in both cast iron and aluminum.
The Dart aluminum blocks are so light that I can pick one up off the floor with one finger...
Here's one that I did where I showed the build process:
B2 Motorsports - Cliff Rosson All-Aluminum 331 SBF Build
There's a lot of tricks to the all-aluminum builds and a lot of stuff you have to watch out for...