How schmick will these 4116 devices make my Z80 computer look?

[Dr. Photon]

I wish we had more colored chips!
So resistor packs are sometimes yellow...
optocouplers white...
TI sometimes painted the tops of their old logic ICs silver...
Older Japanese PNP power transistors came in green....

[glarsson]

Back then, I wonder how many soft memory errors that were blamed on alpha particles or cosmic rays were actually caused by electrical marginality.

Probably a lot.
The company I worked for at time also designed and built memory cards for our systems. We had two series of memory boards; series 1 built from 64k*1 DRAM for a total of 1MB usable (32 bit wide plus ECC), and series 2 built from 256k*1 DRAM for a total of 4MB usable (32 bit wide plus ECC). All DRAM from the same manufacturer. :-) A typical system had 32 memory boards. The paranoid part was a processor on the memory controller that scrubbed the memory for bit errors. It was repeatedly accessing idle memory sections to catch bit rot before they no longer could be corrected using ECC. Cosmic rays? Marginal timing? The answer is lost in history ...