you can see in the chart by 1972 the HP dropped significantly and by 1976 the numbers were 1/2 what they were in the early 70's.
Year Engine Vin Code Engine Letter Code Cubic Inch Rated Horsepower Rated Torque Bore & Stroke Compression Ratio Oil Pressure
PSI
1968-1969 None None 472 375 hp @ 4400 rpm 525 lb·ft @ 3000 rpm 4.300 X 4.060 10.5:1 33
1970 None None 472 375 hp @ 4400 rpm 525 lb·ft @ 3000 rpm 4.300 X 4.060 10.0:1 35-40
1970 None None 500 400 hp @ 4400 rpm 550 lb·ft @ 3000 rpm 4.300 X 4.304 10.0:1 35-40
1971 R 61E,Q 472 345 hp @ 4400 rpm 500 lb·ft @ 2800 rpm 4.300 X 4.060 8.5:1 35-40
1971 S 61E,Q 500 365 hp @ 4400 rpm 535 lb·ft @ 2800 rpm 4.300 X 4.304 8.5:1 35-40
1972 R 62E,Q 472 220 hp @ 4400 rpm 365 lb·ft @ 2400 rpm 4.300 X 4.060 8.5:1 35
1972 S 62E,Q 500 235 hp @ 4400 rpm 385 lb·ft @ 2400 rpm 4.300 X 4.304 8.5:1 35
1973 R 63E,Q 472 220 hp @ 4400 rpm 365 lb·ft @ 2400 rpm 4.300 X 4.060 8.5:1 35
1973 S 63E,Q 500 235 hp @ 4400 rpm 385 lb·ft @ 2400 rpm 4.300 X 4.304 8.5:1 35
1974 R 64E,Q 472 205 hp @ 4400 rpm 365 lb·ft @ 2400 rpm 4.300 X 4.060 8.5:1 35
1974 S 64E,Q 500 210 hp @ 3600 rpm 380 lb·ft @ 2000 rpm 4.300 X 4.304 8.5:1 35
1975 S 65E,Q 500 210 hp @ 3600 rpm 380 lb·ft @ 2000 rpm 4.300 X 4.304 8.5:1 35
1976 S 66E,Q 500 190 hp @ 3600 rpm 360 lb·ft @ 2000 rpm 4.300 X 4.304 8.5:1 35