http://www.fastenal.com/catalog_pages/2005/0159.pdf

Square beveled washers are specially designed for
shimming and leveling in structural applications. Use with
American standard beams and channels that have 1:6 slope
(the same taper as a standard I-beam). Plain Malleable
washers are for general applications.
Beveled Washers
Malleable - Plain and Galvanized

Not perfect but close enough to work with, I'm grinding to slightly modify and narrow the shape. Also using a brass washer between the intake and the beveled washer.