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B6 B7 block differences

There are couple of physical differences between B6 and B7 blocks.

B7 blocks don't have the breather ports (#3 and #4 on the illustration) and the opening in the block itself are filled in.

The timing gears on the B6 blocks are drilled through and it looks like the use oil channels for lubrication (sort of like crank bearings). There's also an extra hole that matches a pin on the back of the drilled gear.  B7 blocks have solid gears and use actual ball bearings.

There's also a slight difference between the middle timing guide, the -AD part number on the post vin -200000 do not have a locating pin that matches a hole in the block:

Pre -200000 block (early 2004) with guide that has a pin (-AC part number i think)

B7 block with the middle guide

B7 block timing side