If they both have 250,000 miles on them, I wouldn't buy either one. If they both are still in the trucks, then you should be able to start them and listen, oil pressure, etc. etc. I would buy the best engine, lowest mileage, etc. If all equal, I would go with the 360. Heads will be the same. Maybe you buy the fuel pump eccentric kit from hughes, install your LA motor timing chain cover and leave the cam alone. You will need a different intake for the magnum motors.