318 head thoughts....

Currently running a 73 318, with a Street Demon 600 cfm carb, Comp Xtreme Energy 268 cam, hooker 1 5/8 headers, 2.5" piping, with Dynamax Ultra Flos on my Duster. The intake is an Edelbrock Performer, converter is 2500 stall, 3.21 geared 8 1/4. Currently running stock cleaned up heads, stock valve size. What do you guys think about pulling the current heads off, cleaning them up, adding 1.88/1.60 valves, and running a .028" thick head gasket? Just thinking aloud. Always looking for ways to get more. Makes at least 275 horse now, and at about 43,000 miles since the rebuild 5 years ago. Still burns no oil and has good oil pressure.