MSB, Middle, and LSB slices. Different because MSB shows Overflow. LSB hosts control switches.

This circuit could be a lot more compact with 74HC153 dual 4Way MUX.

If you don't mind using the magnitude comparator chain to invert logic, T00 can be grounded.

If you don't mind losing identities and asymmetrical functions, T01 and T10 can be tied together.

XOR can fake lost identites. Abusing ADD to invert B restores the lost asymmetrical functions.

So really, no functions are lost. Just easier to wire, at cost of more difficult to explain.

I wired as 3P2T, one 4way flows backward of the original relay drawing, so there is a spare 1P2T per each MUX. Could be chained to detect A=0 and B=0 if either might be useful. I've grounded those spares for sake of low spaghetti.

One mistake I've noticed already: Result 0 might also represent Odd, but definitely not Parity.

I notice LED Bloom misbehave and overwash at certain angles. (Win10, Steam, Titan X Pascal)