We'll I've been busy working out more details of my design in Logisim.  I was finding it very helpful to think through my design by building the schematics in Upverter.  I was working on the instruction decoder and was finding myself needing to figure out some logic.  I was scribbling on paper to try and work it out when I thought I'd try and use Logisim.  I had never used it before and didn't really want to learn another piece of software.  

Wow,  I'm sure glad I did.  What a nice little program it is.  I should have listened to @roelh 's advice to begin with.  It's been really helpful in working out the details of the design.  It doesn't have a library of standard IC's so I started my own library of the chips I'm using.  I used the schematics from datasheets.  I put in Schematics for for the 181 ALU and the  193 up/down counter that I'm using for my registers.  Logisim does have an up/down counter in it's library but I built them from the schematics so I would hopefully simulate the same behavior.  

I'm getting close to finishing the whole design.  I still haven't received all of the components I need to start building on breadboard, but maybe it's not such a bad thing to be forced to do only planning before actually wiring anything. 

I'll add a screen shot of the main circuit.  If anyone's interested in the files let me know.