.100" off the heads is quite a bit. I suggest you check piston to valve clearance with that kind of change. Compression will most definitely increase since you are reducing the combustion chamber size. The only way to know for sure by how much, is the cc the chambers on the heads after the machining work is complete. Have you considered the impact of head port alignment to the intake ports as well? I am sure there will be some mis-match. As mentioned above, an adjustable pushrod checker is the best way to check geometry. I actually made one using an old pushrod by cutting it in half, threading both sides and installing a stud in one half. Pretty easy job if you have a hacksaw and can turn a tap relatively straight. Hope this helps!!
