I got my parts in hand, and finished the clock circuitry. Everything works as expected there. However, I have to jumper my break signal to ground since it goes high when not connected to anything. I did make a few mistakes in the silkscreen - I got my RUN/STOP labels backwards and my clock selector of FAST/SLOW backward. Not a huge deal, but still annoying.
I also started on my control circuit. I found I had to have a lower value pull-down resistor on my reset line. It was sitting around 1.4V, so it was being read as a logic high instead. TTL has internal pull-ups, so I have to overcome that if I also want a pull-down.
And then I discovered that I got my read/write signals backwards. And looking into it further, some places on the board are correct and some places incorrect. So it's a big mess that I have to fix. I think the root of the problem is the active level of TTL is low, and I'm very used to thinking active high. So I got them swapped when I labelled the nets. I'll have to start figuring what traces need to be cut and patched. This will keep me busy for a while.
update: I have to cut 5 traces, and run 5 jumper wires. I have all my cuts done and 3 jumper wires in. I'll add the other jumpers when I do those chips. Fortunately all the jumpers are on the bottom side of the board, and all go to pins of through-hole sockets. Not a big deal, but still annoying.