overheating problem from day 1

I am working on a 1983 B-2000 2.0 liter gas truck and with a New radiator it will not go 2 city blocks without pegging the heat gauge and blowing the overflow line to the coolant tank. We had the old radiator rebuilt and the owner thought that a new one would be better. No such luck. It will get to blowing it's top in 1-2 blocks. Any help on getting the air bubble out of the block and/or head would really help us out. It has all new hoses, rad, and thermostat. Thanks for your time.

Jack up the front end and run it with the cap off. That should help.

Also, I'd change the radiator cap and fan clutch operation.