Brian Burwell shared the attached photo’s of his repower of a Farmall 300 with a Detroit Diesel 2-53 and of it’s conversion process.  I’m attaching them with his permission.   Great looking tractor and conversion!  My notes show a 2-53 will have 45 hp @ 2000 rpm, and 41 hp at 1800 rpm.  With N-50’s I would think it could pull close to  50 hp with some smoke.