I am running 1mm larger valves with bronze guides. Intake seats are .050" and the exhaust is .080". Heads are ported to take advantage of the larger valves but is a conservative job. May lap line is not in the aluminum but at the edge of the seat insert. My intake valve guide clearance is .001" and exhaust is .0015" if I rember correctly. I had the heads off after 1500 miles for inspection and to try some new valvetrain componets. No abnormal wear was found so I am still running this setup. The engine is supercharged and makes a conservitave 553 rwhp at 6200 rpm with 13lbs of boost and no intercooler. I do attribute the ability to run this valve setup to the increased control of the tighter bronze guides. I did state above that with out the proper port work that yes just putting in larger valves would be a hinderance. I do know that my engine pales in comparison to yours and that you have a far greater wealth of knowlage than me, but I am just stating my own findings. I have attached a pic to show my valve seats. These are 97 heads.
63.5 KB Views: 306