We had an 800 CCA (group size 7 battery in our car which needs replacing but the closest they have is 750 CCA. It still has the sideways terminals and looks identical to the one I removed from my car, it'* just 750 CCA instead of 800. Would this be OK or do I need to keep looking?

Sounds to me that any side terminal post battery group 78 should fit in, and then you should be able to find 800CCA +
The longer lasting deep cycles batteries today are now called AGM. Absorb glass mat, perform better in the cold last longer, & better sealed, so you wont get any terminal corrosion.
AGM = look for. Napa, AGM Exide AGM ,& the best Odyssey (which is virgin lead) are tough to beat.

Also I'm not a big fan of side post batteries due to the fact of a smaller contacts & sometimes difficult to access.
I converted my Buick PA to a top post easily. The blue battery is an Exide AGM.group 34 top post only.

I also have an Odyssey battery, the most powerful battery period,= tested on midtronics load tester at 1200CCA new.
The 34/78 DT (dual terminal) with side posts can last 10-12 years.

Yeah, 750 is okay. If you're in really cold weather you'll probably want the 800 instead for some extra margin.

I admire the work you keep your park avenue nice with. My car started dirty and rusty and a little rough around the edges so I have not made an attempt to make it perfect but my next one will

i have a north star and brass terminals. I recently found brass nuts. You don’t have to worry as much since you detail your engine but it’* An added bonus.

also, we both should DEFINITELY get the gm battery insulator they had from factory. Heat is killing our AGMs because they are denser and they are already under hood which gets toasty

I can see your wiper arm is bent @Soft Ride i can’t find em under 40 unfortunately

Thanks, I try to keep it clean. It'* still driving well after all these years & batteries are still working ok. Am at 9 years I think on the Odyssey.
Yours is much better than many I've seen. I remember once at a gas station the guy next to me also had a PA & when I lifted my hood to check the oil his jaw dropped.
Hey bud he says, how did you keep it so clean under the hood? My reply was hard detail work, power washing & LPS Pre-solve de-greaser. His had never ever been cleaned.
The wiper is a bit bent but still swipes ok too.

one night I was driving and the splines sheared on mine and it went crazy all over the windshield before I could stop the motor which it just kept flailing bexauseit spun freely and I was going 70. Stopped at a gas station, bought a pliers, loosened nut a bit more, set it back close to where it should be at park, and tightened with everything I could. I used a socket when home..it’* holding fine, but it got twisted a little worse than yours and unfortunately the angle it holds a blade at is steep and it makes my silicone blade not do too good... but at low speeds it’* too steep and water will actually jump over it in parts. At speed it’* fine. I still have good tension, I was considering bending the j hook end of the arm the opposite way to counter rhe twist at the base by the pivot... wanted to do it when I have a line on a good used one first.

mine is superficially clean. I sprayed with a washer, I painted parts that had lost paint. But no shiny plastics amd lots of wear. Engine had been in and out in different hands,. Splash shields are missing and firewall has slight burns, etc.

runs like a clock tho, no oil burning 225k.

if not for unibody rust I’d be keeping it better but I’m just gonna do what is reasonable until it dies then I’m taking the good stuff with me to my next one

it’* not too bad from a distance tho

Yeah, looks like a nice one!