Replacing a 273 motor for a 5.9 360 Motor Question

I would like to know what type of problems i will have if replacing a 273 motor for a 5.9 360 motor. The person I am getting the motor from says it a complete motor. Will the motor mounts match up, with the headers mount up, with the bell housing match up. Or what else am i looking at to replace the old tired 273 motor...

Thanks