This information is from Tractor Data
John Deere 430 Power
Drawbar (claimed): 27.1 hp [20.2 kW]
PTO (claimed): 29.2 hp [21.8 kW]
Drawbar (tested): 26.15 hp [19.5 kW]
Belt (tested): 28.31 hp [21.1 kW]
John Deere 420 Power:
Drawbar (claimed): 20.31 hp [15.1 kW]
Belt (claimed): 24.83 hp [18.5 kW]
Drawbar (tested): 26.15 hp [19.5 kW]
Belt (tested): 28.31 hp [21.1 kW]
John Deere 40 Power:
Drawbar (claimed): 16.77 hp [12.5 kW]
Belt (claimed): 21.13 hp [15.8 kW]
Drawbar (tested): 22.9 hp [17.1 kW]
Belt (tested): 25.2 hp [18.8 kW]
This information i from searches on the net.
As you can see from above there is almost 10 horse power difference between a JD 40 and aJD 430. So that will make some difference. All three have the same PTO that has an RPM of 540. So only difference there is Horse power at PTO.
General rule of thumb is: Bush hog is 5 horse power per foot. So JD 40 would run a 4 foot, a 420 would run a 4 foot and a 430 could run a 5 foot.
Plows: 1-1.5 hp per inch as a guide. So a two bottom 14 plow would work on the JD 430. The JD 40 co0uld pull a 1 bottom 16? while the 430 could pull 2 bottom 12?
Disk: all three should pull a 6 to 7 pull behind.
Soil condition is a big consideration in all the tractors.
I hope this is something likec what you wanted to kniow.
In 1951 we farmed a 100 acre farm with a CA Allis Chalmers. Which had the following power
Allis Chalmers CA Power:
Drawbar (claimed): 18 hp [13.4 kW]
PTO (claimed): 23 hp [17.2 kW]
Drawbar (tested): 22.97 hp [17.1 kW]
Belt (tested): 25.96 hp [19.4 kW]
Don