Hotter cam, stiffer valve springs, Q jet reworked, distributor and timing settings, beefed up TH400 with different shift points. The valve size remained the same, not bigger like the 70455 stage1. Higher oil pressure spring and 5/8 inch pick up tube. I believe 2 1/4 exhaust. Standard 3.64 posi, and I think in 69 3.42 posi with AC Chrome valve covers. I don't know about the extra frame torque box like on the 70 Stage1 and big bowl fuel pump??
All the readings say extra heavy duty cooling with larger radiator but I believe it's also upgraded with a clutch fan.