From HG 1970 was the start of trimatic so Toranas, kingswoods, premiers, statesman should have drain plugs about 1979 was when the accountants worked out they could save the cost of a plug. All 6 cylinders and most 4.2 V8 ran trimatics.
I have rebuild 4 ,6 & 8,trimatics they have a few extra plates for the V8's that will be a future project a wild 7k with Tricked V8 trimatic.