a little 318, 0.040" over, with a 4" arm will get you a 392 WEDGE.
Oh, yeah I forgot to mention. I just picked up an ultrasonic thickness tester (Made in the USA) for $5 at the Mare Island Museum liquidation. So much stuff at great prices. They even have a Pratt & Whitney lathe 16"x54". I didn't want to ask the price because I have nowhere to put it. Anyone in the bay area interested? The museum is open on Wednesdays.