Those captive nuts are for the bolts attaching the fenders. Be patient, slosh 'em a few times with some type of oil. I had a hell of a time with mine, some came off with the sheet metal from the body--more patch/repair. You might try some carefully applied heat, then slosh 'em while they are warm. You don't need exotic spray penetrants for this, heavier oil is probably better, higher flash to fire point and all.... :p
