I would remove the fuel pump, and not plug the hole in the front cover. pour about one ounce of fuel down the carburetor and start the engine. If the squeak is gone, you've narrowed down the source of the problem, somewhat. With the fuel pump on the bench, actuate the arm and listen for the squeak. if you hear it from the full pump, that could be the problem, but I doubt it. Hopefully, when you ran the engine with the fuel pump removed, you got a big mess of oil coming out of the access hole. If you got little or no oil squirting out, I suspect that you are not getting oil to the front of the engine and that the eccentric that drives the pump is dry and squeaking, (along with your new timing chain and gear.) To help verify this, apply a dollop of grease to the tip of the pump lever where it contacts the eccentric and re-assemble. Start the engine, and if the squeak is gone, you've narrowed down the problem further. It's not fixed; the squeak will return. You'll have to dis-assemble the front of the engine to determine why. Perhaps the cam shaft retainer plate was improperly installed. Study your Shop Manual! As far as break in, it is imperative that you load the engine in order to seat the rings. By that I mean drive the car to get the transmission into top gear and then accelerate just hard enough so that the transmission doesn't drop down into a lower gear, up to about forty five or fifty miles an hour and then back-off. Repeat this about a dozen times. Also, you may want to check the break-in procedure in your Owners Manual. Make sure that you're using a motor oil with a HIGH ZINC CONTENT. Closely monitor oil pressure and temperature to make sure they remain within specifications, and shut the motor off immediately if they don't. Don't break-in this motor on a hot day! As far as a vacuum leak, how does it idle? Is it slow and even? Short out the sparks plugs one at a time, while at idle. The one that has the least effect could be an indicator. Remove all eight spark plugs and compare their appearance. The off color one could be a clue. Acquire a vacuum gage, and learn how to use it. Also, do a compression test. The lowest cylinder could point to a problem. I've given you enough to ponder for now, let me know what you find. Good Luck!