One -- The sound is OUTSIDE of the engine internals, as mentioned.
Two -- A High Volume oil pump will NOT increase oil pressure that much. Putting the high pressure spring IN the pump will. Even with a stock pump, the spring can be shimmed a bit to increase oil pressure. No real harm in that, but might take a few more horsepower to run the pump. Generally, not an issue. Reasonably easy to change, if desired, as the oil pump is external to the engine block.
Three -- A flat cam will cause other performance issues than those displayed.
Four -- The trans leak could well be the seal the torque converter slides into, on the front pump. A hard, aged, seal might not like the way it was done. W
ill require transmission removal to fix. Really not unusual on an older car.
At the present time, the worst thing I see is the transmission leak AND where it is coming from. There are a few likely candidate areas other than what's been mentioned. None hard to fix, just more time and money. Key thing is that the transmission operates normally!
IF you are not comfortable with the seller's information, find another car, period. YOU have to be comfortable with the purchase. There can be NO real advantage to getting into the Chrysler side of the vintage car hobby with a 440-engined car. A Fury III 318 car can be just as good, for example. Or a Newport 383 2bbl, for that matter. There were several Fury III 318 cars at the recent Mecum auctions, for example. Some under-appreciated cars in the C-body realm of things. Might not get the "OOOs" and "Ahhhhs" a 440 might, but still good cars to enjoy driving and being seen in. It was mentioned decades ago, that "simpler" cars usually don't have as many options to cause issues as the cars age. Things like power windows, power seats, power antennas, which higher trim level cars can usually have. BTAIM
From looking at the auction results from the more recent Mecum auctions, it appears that their selling prices are softening and flattening some. Which can be good for the buyers! You can do a free registration at
www.mecum.com to get that information and keep up with those numbers. Facebook Marketplace can be a decent place to find cars, BUT many are just "used cars" and the prices tend to be higher than what I consider "normal", in many cases.
In the mean time, please understand that Chryslers of the "Slab" orientation ('65 to '68) are some of the best designed cars on the road, then and now. The bodies are very strong and solid, but rust can still happen over time. The powertrains were at least as good as anything Ford and GM did back then. Those general model years were when ALL of the OEMs had finessed their earlier engineering to be more bullet-proff and long-lived, so it can be a "sweet spot" of sorts for all of them, but the Chrysler products (IF opotioned correctly) were generally the best, from what I saw back then and us having a '66 Newport Town Sedan I took to college and drove after that. We bought it at its 1yr birthday and 7100 miles. With ultimately over 150k miles and very little mechanical work needing to be done (and, its OEM-production ball joints). From day one, it was a cherished member of the family, but not "ocer-maintained" either. It just worked.
ONE observation, it is much easier to find somebody to work on Chrysler products than it is for similar Ford and GM products. KNOWING the engineering and WHY it is better than what others did is the key. There CAN be many similarities, but the "fix" in non-similar areas can flumox some otherwise-good mechanics. Back then, the cars were NOT "generic", as each OEM had their own orientations and goals to hit for what they wanted the cars to be. Like a good GM mechanic is "lost" on any other brand of car. Some good Chrysler products have been scrapped due to these things!
Personally, I prefer the Dodge and Chrysler brands of that era. Plymouths, as good as they can be with nicely-optiioned cars, tended to be a bit less robust in some areas, but still with the general "Chrysler Corp goodness" of design and execution, which made them such good used car values, back then.
In your learning, find Chryslers you can TOUCH, FEEL, Drive, and experience. Even if you might need to drive a bit to do that. "Education" and appreciation are important! You might discover that staying with Ford and GM is where you feel best. You might also discover how much better the Chrysler products could be, too! They ALL feel different (some better, some worse) in many ways. NOTHING generic, especially back then.
Just some thoughts and observations.
Enjoy!
CBODY67