More advice desired on my Model Railroad Building light controller circuit
The circuit below should do what you want.

It works by inverting the output of the 40 bit shift register chain, a bit at a time, and then feeding it back to the input so that the data in the register recirculates forever, inverted each time it goes through. 

One caveat is that since you're not using an MCU and the chip has no RESET, if the data in the register comes up as something other than all zeros or all ones on power-up, the pattern stored in the register, and its complement, will circulate forever.  Not necessarily a Bad Thing, but if that happens the lamps will never be all on or all off at once.