He means taking the heads to a machine shop and having the surface that goes against the block shaved down by 0.045". It makes the combustion chamber smaller thus raising the compression ratio.
IMHO you are making changes to an unknown engine. You knew it worked before with the head gasket it had on there. (Or the valve s did not hit the heads, you could run on pump gas without ping, etc.) With the changes you are making it is unknown where you will end up with tune, drivability etc. I would get a head gasket as similar in thickness to what was on there. If you are using a cam with more lift then what was on there before you might want to make sure the valves don't hit the pistons.
Admittedly I'm no expert and others can say with some certainty that your combo will work without checking.
