I again have a lessons learned here. I didn't even bread-board this before just changing the schematic to force a high default. Only to realize post putting it together that nothing works.
First, I do appreciate the input - it was exactly what I asked for - learning why things didn't work as I expected. And yes, this is old 7400 series stuff - it still shows huge holes in what I thought I knew, so I'll keep on "hacking" on my simple 7400 CPU until I get all the basics down.
Of course the issue here is, the the 74151 is a multiplexer - based on a selector a given input signal is selected and send to the output. The way your quickie diagram shows it, the LED now shows the negative (complementary) of the signal going into the selector - that's definitely not what I wanted. The LED is the indicator of what the selector is set to - and us humans like counting the "on" vs. the "off" to see if things are active.
It's not a problem if the switch is "turned on" when you actually break a circuit - as long as the LED follows.
Another issue that I'm now hunting on bread-boards is that regardless of throwing the switch, I still get almost 5V on the selector signals. The LED turns on/off just fine, but the signal that controls what happens doesn't change to low. When I measure the pins with the volt-meter it keeps showing a 4.7v potential on the selector leg, even though it should be forced to ground. I wonder if connected the 330ohm resistor the the 4.7k ohm that gets pulled to ground would make the LED follow the input signal. Well, time to test ...
So lesson learned, don't just change the diagram with out testing it first. Or rather, even if the change seems simple you should still test. I do that for software - no clue why I didn't apply that for hardware too.