engine swap

is it possible to replace a390 with a 460 with no modifications? I have a 1971 F250 camper special 390ci,C6 autimatic transmission

Wow, now you've got me thinking back! If I remember correctly, all you may need to change are the motor mounts. As far as I can remember, the bolt pattern (engine block to transmission) is the same. If you do this swap, make sure to compare your flexplates, to be sure you'll be able to bolt it up to your torque converter. Best of luck!