If the gap really concerns you, just epoxy thin flat washers to the front of the block. If you're as OCD as some of the guys here, you could have a machinist set the washers up on a magnetic surface grinder platen and grind them to a perfect flush fit with the rest of the pump mounting surface before attaching them to the block. That would cost approximately three times what you spent on the plate, though! A little blue LocTite will stop any seep leaks from the bolt threads, or you could install studs, not bolts in the drilled/tapped holes in the block and use threadlocker on them for a permanent installation. Tighten the nuts on the studs every couple of weeks if you want to after that.
Jerry
