11/32 valves in X heads

I picked up a set of X heads that had a half done valve job. They are bare, and have had the seats replaced, but not cut, and the guides are sleved down to 11/32nds. My machinist is putting in chevy valves. With the stock 3/8 stem valves being 4.980 length and the chevy stuff being 4.911, is my only option a longer pushrod, or do I need to get 273 adj rockers and shafts? I asked about getting the + .100 chevy valves and grinding the stem tips, the machinist said it wouldn"t work... How do you adjust valve lash on a hyd lifter with the motor running?