As far as simulators go, one could of course use a full HDL language and simulator (such as GHDL, or Icarus Verilog), and while I am doing some of that for this project I decided to check out Logisim's descendants Digital and Logisim-Evolution. Work on the original Logisim has stopped, and it's up to the community to continue it - fortunately, multiple groups have continued its...well, Evolution. 

I started by checking out Digital, and after scanning through the issues it looks like the ability to draw a custom representation for a circuit is not yet available (although it is in progress); Logisim-Evolution has this feature, so I went with it. After looking through the issues on Github, it appears that the simulator's core would require some serious refactoring to support true bidirectional pins - then again, V1 of Chisel didn't support tri-state pins either (whatever that means - I never bothered with Chisel).

Anyway, it's what I went with (along with VHDL/Verilog, but it's likely easier for people to follow along with if using a tool like Logisim Evolution).

But here's the deal: THIS is the tutorial that everyone needs to see. It's what sold me on Logisim Evolution, for the same reason the author states - the other tutorials will put you to sleep, let's see something real, fast.

LEGIT. 

Ok, next we're going to add some items to our References section:

• A Microprogramming Learning System
  • https://ir.library.oregonstate.edu/downloads/vx021j62g
    • This is an abstract for a Master's Degree about using the AM2900 Evaluation kit we got the schematics of previously, and it mentions some improvements and extensions!
• 27S03
  • There is a memory chip, the 27S03 that's called out on the AM2901 Evaluation kit; what do you know? There's an alternate part called out in the TI TTL Databook (the SN74S189).
    • http://www.bitsavers.org/components/ti/_dataBooks/1976_TI_The_TTL_Data_Book_2ed/02.pdf
  • Well we can't find that part, it's unobtanium (like the original AM27S03). But knowing what we know about these logic families, "SN" is TI's manufacturer code - what if we look for just "74S189"? BAM:
    • https://www.jameco.com/z/74S189-Major-Brands-64-Bit-16x4-Tri-State-RAM-DIP-16_48557.html
  • In searching for how to use Logisim Evolution to model this, I came across a video that was really straightforward - super legit, check it:

Cool stuff!