If you go too big with a motor you will explode the back end. I wouldn't go anymore than say 20hp above the previous rating motor. A 6 cylinder truck motor, International, many of them just bolted in. With others you will have to change and make up the swage plate.
Don't forget the motor has to fit between the side rails.
There's also the possibility of some of the International combine motors will actually fit right in.
Can you get one from a wrecker, that would be the way to go.
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