Delivery date on the owners service policy...June 26, 1956...The day the music died (on East Grand Ave.)

'56 Caribbean htp and '55 400 way overpriced for the mess that they are. PB

I'd be very wary of that '51 300. Some of those pics are old, like when they got the car, and some are current. Ad says, "pretty chrome" and "perfect glass". Neither of which is true. Windshield is broke to hell and rear bumper is severely pitted, cormorant is missing. Floor pans are shot and if they are that bad, you can bet the hog troughs and rockers and dog legs are bad or have been fixed over. Don't even think about buying it without "in person" inspection. PB

You definitely have overhead noise. Lifter and valve stem/rocker arm clearance issues. This could be caused by poor oil pressure, stuck lifters, collapsed lifters, worn cam lobes due to lack of lube. You do not have connecting rod, wristpin, or crank noise. You definitely need to check oil pressure and remove your rocker covers and visibly check your rocker shaft movement and how much oil is dripping off the rocker arms.
As info, main bearing noise is a deep heavy clunking sound with rod bearing noise a lighter clunking sound. Wristpin noise is usually a "clatter" and is generally heard when backing off on the throttle. Wristpin noise generally goes away when accelerating.
Any COMPETENT mechanic should be able to diagnose and repair your issues for you, provided the parts are available. PB

p.s. I would NOT continue driving your car until repairs are made.

Did you grind your rings to obtain proper gap? .0045"/inch of piston diameter on standard cast aluminum, .006"/per inch of diameter on hypereutectic pistons. Did you lube piston packs when installing?
Battery condition and starting motor performance are important. Replace that headgasket. While the head is off, squirt some oil on top of the pistons, and crank engine and see if it is still cranking hard. If it is....start over, something is wrong.

I think you are confusing a 22nd series engine serial# with 1948 only. In fact 22nd series went into 1949. Engine casting date being Jan 1949 suggests that the engine probably went into a 22nd series car.

We obviously responded at same time.

I bought my '56 Clipper Deluxe from the original owner in '75. On the N.J. title it was listed as 1956 Packard Clipper, sedan, green.

It has the Packard insignia on the lower right side trunk lid. It also came with the senior steering wheel (I don't know if it was dealer installed or not).

I would NOT mill more than .030" off the head. you will loose breathability in the crossover area. Are you milling because of pitting, flatness, or because you think you're going to get a significant increase in comp. ratio? If the latter, there will barely be a discernable difference. If you've got performance experience you might notice a difference/ Most will not. It was a good running engine as designed and with the fuel that was available. The flathead design has it's limitations.

What is shown in your pic of the bearing race (cup) is "spalling". That is metal fatigue, not rust pits. You need a new bearing and race. Your current bearing and race is a failure waiting to happen. First,the diff will start to growl, and then maybe a bearing roller pops out of the cage and finds its way in between the pinion and ring gear. Then you've got all sorts of problems. And expense. Do it once,and do it right.

Many moons ago we used 90w pure mineral gear oil, in diffs, which is what it was designed for. You should be fine with 85/140, like was said above, or a RedLine "heavy" lube. Just a note of caution, the modern EP (extreme pressure) additives, over time, will degrade brass or bronze, so be wary of bushings
or maybe side gear spacers etc. in application. pb