If the actual curved shackle brackets collapsed, I can't even begin to think of what massive forces must have been responsible. Just beyond understanding at this point. If so, damage elswhere can be anticipated.

Kind of reminds me of this ad I saw a while back of a car for sale:

FOR SAIL: 1938 Parkard convertable phaiton, duel cowl, body by Durham. An all original car with new lacker paint job (wheels in primor) and rebuild engine. Ruffly 28,000 original miles, engine idols smoothly. Chrome shows very little ware. Correct mohare interior threwout, slight tare in door panel. Has had recent break work, rebuild carbarator and vacum wipers. All the guages work. Rear springs a little week, gas peddle broken, and the rear axel has a little wine. Missing the trunk handel. Comes with a rumple-seat coupe parts car. Asking $38,000, diposit required. Garraged-kept, a real steel at this price.
No warrenty.

OK, got your email and sent the picture moments ago. Hope it proves helpful.

Bob, why don't you just browse the 48-54 parts manual available on this website. There are about 32 different cylinder heads listed, a few too many for me to type out. For 1954 the standard heads (excluding export and specials) were 7.7 for the 288, 8.1 for the 327, and 8.7 for the 359.

I did offer you a copy of the rear leaf spring shackle from the 1951 Serviceman's Training Guide. Were you not interested in same?

I have no idea how accurate they are, but one thing is for sure, taxi cabs and 6-cylinder export cars weren't the route to regaining their luxury car status.

John, geez you're like a dog with a bone! Give it a damn rest, will you! And don't forget that the Studebaker Club printed it first in their "Turning Wheels". So I guess you're calling Studebaker people just as stupid?

I was just browsing the "Serviceman's Training Book" for the 24th Series Packards, published in August 1950 and see that it identifies the engines as "Thunderbolt". So my guesstimate that the timing of the trademark was about 1953 is obviously incorrect.

If they were put on at about 65 foot lbs and allowed to rust, it's going to take more than that much to loosen them. I'd suggest PB Blaster as the best rust-buster on the market, and a breaker bar. I wouldn't use an impact gun.

TW, is the casting date on your head also 1951? I may easily have been incorrect thinking that 1953 or so was then the trademark began to be used. But as others have pointed out, many cars still have original engines but have had cylinder head replacements over the years that I don't think that's a reliable indicator. But it seems we can either find out thru the Patents and Trademark Office when Packard registered "Thunderbolt", or just start collecting casting dates on heads that have "Thunderbolt" cast into them. Sounds like a fun little project for someone to collect data on.

My 1948 Custom 8 had a replacement 356 head with a 1951 casting date (factory replacement with 14mm spark plugs) and doesn't have the Thunderbolt on it so I'm inclined to think the Thunderbolt trademark was later than the end of the 23rd series.