All 225's make about the same power. What you are mistaking for less powerful engine starting around 1972 is just the way engine output was calculated as dictated by, I think, can't recall exactly, it was American Society of Engineers; ASE. This revised method became the new standard which American engine output has been measured until recently; I believe the formula was tweaked again. (someone with clearer head may chime in on this... I hope)

Pre 72 (or so) output was measured with just engine and maybe water pump, post 72 or so accessory losses were factored into calculations. Such as power steering alternator etc. those devices take energy to turn which subtracts from that 145 HP you are seeing listed as stock output.

Factor in the drive train and these engines in stock tune they only make about 95 hp. at the rear wheels.

If you want a true 145 hp, and stock torque number as listed in the old literature at the rear wheels, one needs to make some changes to compression, cam, carburetor, head breathing, and exhaust size.