I owned '73 and '74 Colonnade coupes and while they were nice cars I can relate to what you've written. Most notably with both of them was drivability issues when first starting out in humid conditions. Post '75 G.M. vehicles I owned were less problematic in that regard due to what you've described and I'd imagine the high energy ignitions.
With respect to the article John posted I seem to remember reading somewhere that the 455 in the Trans Am was dropped after '74 only to be reintroduced during '75 due to customer demand. At 200 H.P. it was basically the station wagon engine and a drop of 50 H.P from the '74 offering. Interesting article as I didn't realize an emissions choked (as they all were) 360 in the '76 Dart could achieve such a high speed.