The 051 is a cast iron unit that works with a vacuum retard throttle valve. The vacuum port on the throttle valve should be on the bottom of the valve.
If you have vacuum ports on the sides of the throttle valve it's probably a constant vacuum system. You will need to match the distributor to the throttle valve.
The 062 unit is about 20 degrees of advance by vaccum and about 10 degrees by mechanical flyweights. The 051 is 20 mechanical and 10 degrees vacuum. These two systems won't interchange with each other and are not to be mixed up.
