Test fit the pan over the oil pump before installing it. It will usually prevent the bottom flange from resting flat on the block (the flat gasket surface without the gasket). It will only be like 1/8" gap. I usually then use a ball peen hammer on the inside lip of the oil pan to bang it and make some clearance for the pan. Trial and error. Pound a bit, then test fit. Pound a little more, then test fit.
I like to get it to the point where the oil pan can rest on the gasket surface of the block without the gasket. That way it will be fine with a gasket.
The melling HV oil pump is a good pump. I've put over 250,000 miles on one or two of them.
