"Helper" leafs and coil spacers will help in the short term but ride quality suffers greatly as the springs loose their ability to support the car.
Best solution is to replace with new.
There are a good number of suppliers available.
Let's see photos!

Impressive. And that is a truly diabolical gauge :)

Got one if interested. $150.

" I even tried prying it up with a 3’ pry bar but it doesn’t budge."
Then try a 6 foot bar, it's just stuck.

Those core plugs must have been a serious challenge to do while still under the hood? I shudder to think.
The small number of exhaust manifolds that I have handled seemed to be pretty high grade cast iron, surprised to see your looking so rough...
I had one on ebay for more than a year, it was perfect. Finally knocked it down to like $29 to get rid of it.Don't let someone bone ya like $100...

I have a '55 which has to be close, but I am a long way from Texas. (MKE)

Bummer, that is a rusty push rod :(
The engine may be worth more in parts if you are inclined.
The PS pump, Dist, Starter, carb should be easy to sell.

Spring cleaning time.
Have 2 nice thermostat housings, some pitting under the hose but very solid, $25 Ea.
Alum timing cover, clean, good threads.
$45
PM for photos.

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Watching... I need some engine paint.

It is the same story everywhere...
I was talking with a Proctologist recently & he said that even he was short handed!

Longest journey start with single step...
How does the sheet metal look?