i wanna put a 9 inch in the 65 f 250 i have what donor vehicle will give me a good start

 

If you're really wanting to swap in a weaker rear end than what you've got, look for a 1964 or later rear end out of a F100 or F150. The heaviest rear is rated for 3300 lbs. Use the axle tag and/or outer axle bearings for identification. You'll probably have to relocate your spring perches, possibly lengthen the driveshaft, buy a u-joint to adapt from your 3/4 ton driveshaft to the 1/2 ton rear, and adapt the brake lines. By the way, you're also getting smaller (weaker) brake shoes. Good luck!

 

The question really is if you want to make a half ton truck out of a 3/4 ton truck. 9 inch axles are good axles, but the axle under your truck now, probably a Dana 60, is definatly stronger, and is generally cheaper to modify.