perhaps the guys at fed ex just didnt feel like being bothered filling out the paper work and made stuff up so the customer didnt want to send it through them.
Seems like your jumping on the OP.
Great time from a stock 318 ! The stumble could be fuel spark or could be the valve springs giving up. A stock teen wont wont to rev to high anyways. If you plan on some mods start with ignition and exhaust.
It will probably run best at around 16 to 18* with your total at 36. Disconnect the vacuum advance. Make sure the plug wires are in good shape. Then start tuning the carb.
Check the float level, power valves and make sure the carb body and base plate arent warped. I know you've tried other...