The 351 Windsor will have oil consumption problems if it’s installed in an Econoline van without the right intake gasket. The bottom of the intake manifold was too hot, even with the metal heat shield riveted to the bottom of the intake, so Ford left off the shield and used a special “bathtub” intake gasket to keep the oil off the manifold.
This intake gasket was used on all of the 1974-’80 E150/250/350 vans and on all the 1981-’87 E250/E350 models with 8500 GVW or higher. It was discontinued when Ford put fuel injection on the 351W in 1988. This special gasket isn’t included in any of the gasket sets provided for this engine, but Ford lists it as a p/n D7UZ-94333-A, and most of the aftermarket gasket companies can supply it if you specify the right application.
This problem may be old news to most rebuilders, but there are still plenty of these vans out there and lots of installers who don’t know the difference, so ask if the engine is going to be installed in a van every time you sell a 1974-’89 Ford 351W and, if so, make sure the customer has the right intake gasket for this application.