How much to shave off the cylinder head.

My opinion: Measure what you have, then take off the needed amount (either deck, head or both) to get between 8.7 and 9-1. Use the numbers for an "aftermarket" head gasket, (as the OEM stamped steel gasket is getting hard to find). There is absolutely no downside to raising the CR of a slant, within reason. Helps with power, and fuel milage.
With a 225 engine there is no issue of piston to vale clearance, unless using aftermarket "race" pistons, or are doing excessive milling, and using a big cam.
With a 170 engine you need to be careful, as the pistons come to the top of the cyl in stock form.
With .100 off the head/deck should be ok on pushrod length, but should still be checked.