Using, learning, programming and modding the Gigatron and anything related.
We do have an inverted clock, but it's also created by an inverter (U1). You can try and characterise a 74x241. One of its enable pins is positive, the other negative. You might be lucky if their propagations are the same, but a quick first glance at the 74LS and 74HCT data sheets is discouraging. Still, this should be a simple test.