Clock logic - 8-bit computer clock - part 4

I very much realize this is a necropost... and maybe its been pointed out, but the 74x157 chip could be used instead of the three other IC's to select between the two clocks and support a halt. We only need to use one bit of the multiplexer; tie the manual clock signal to A0, tie the astable clock to A1 and the selector output to A/B. Then you can tie the Halt to the chips enable pin and the output is cleanly multiplexed I will grant that this isn't nearly as popular or easy to get ahold of as the basic logic chips though.