Contrary to popular belief, the critical clearance in a Buick oil pump is not between the gears and the flat plate mounting surface, but it is the clearance between the walls of the pocket and the gears. This is where the oil pressure is developed.
The factory spec for plate clearance is .002"-.007", and even on the loose side, we always have good oil pressure.
A little know fact in the turbo world is the Buick V-8's used a very similar oil pump, in fact the Buick 350 V-8 pump is identical.
In the early '80's when many Buick 455 parts had been discontinued, Mike at TA redesigned and built a new timing cover for the 455 and incorporated many improvements after working with some of the original Buick engineers, and ended up with a superior product.
One of the MAJOR difference between the new TA V-6 timing cover and an original factory cover is the tolerances in the pocket, and of course passages were also changed and improved for better flow as well as increased pressure.
Our experience is that any booster plate in not needed if all else is proper and in good shape. Since the extra gasket is a potential leak, and have replaced many on GN's, I personally do not use them.
When we build a $10-15K engine for a customer, they almost always opt to spend a few more dollars on the "heart" of the beast with a new cover!
