I am doing a head gasket job on an 98 outback 2.5l, I am concerned about the grooves left by the old gaskets on the cylinder head surface. They are also on the block Is it necessary to get them ground by a machine shop? I checked for warpage with a .002 feeler gauge and straight edge and they do not appear to be warped. Thanks

i would, as a rule resurface any head that has a bad headgasket, not for flatness but for surface roughness. irregularities are the enemy. i think what would be needed is a Surf guage

What about the block? I have the same grooves on the mating surfaces on the block?

Not sure if this helps but : http://www.scoobymods.com/forums/showthread.php?t=7229

That is normal, you need to sand them out. Take a nice size peice of plexi-glass (lowes). 6 inches wide by 10 inches long and wrap it in 600 grit sand-paper, the black sand paper. Soak the paper down with WD-40 and start evenly sanding the block. Do not spend a lot of time in one section. It will take some time but you can get all of that old gasket out. If you see some wd-40 dripping down the cylinder wall just gently wipe it out.