First year of 4-wheel disc brakes???

Curious: What was the first year of 4-wheel disc brakes on the Toronado?

'67 was the first year of FRONT disc brakes; when did rear discs enter production?

I'm kinda guessing '76--'77--'78, (as optional equipment) but I don't know for sure.

You are about right, to be sure go to Rockauto.com and see what the first year is they list rear disc parts for.