Status: Studying the classic 74181 ALU chip.

Some useful resources I found:

Library of 74xx chips for Logisim

http://www.righto.com/2017/03/inside-vintage-74181-alu-chip-how-it.html#fn:hackers

http://apollo181.wixsite.com/apollo181/shift-right-with-74181

https://books.google.com.br/books?id=8uTNlPe-s_EC&pg=PA138&lpg=PA138&dq=74181+8+BIT&source=bl&ots=w0xXpIZ4tc&sig=8PbJivB4Ep5j5bZl4v6MH3HgXYA&hl=en&sa=X&ved=0ahUKEwjPyOaumL7UAhXMQyYKHS14CXcQ6AEIRTAH#v=twopage&q&f=true

Hope that helps someone as helped me. This ALU has odd functions, it's not easy to understand it.

I also made a test circuit to make sure two ALUs work well together (remember, 74181 is a 4 bit ALU).

All available on github.