I have had them last for 4 to 5 years. 365 cca and 300 amp normal. less than 8 inches by 5.5 inches. Battery tender when parked very long. Less than 70 dollars.
A friend of mine mounted a PC680 on it's side behind the dash in his Model A bucket. You can mount them anyway except upside down which can help if you're pushed for room. The Odyssey PC680 cost me A$250 and lasted nearly 5 years -my fault as it went fully flat and AGM batteries don't like that. I replaced it with a FULLRIVER Chinese equivalent for A$150 and it's been going for 9 years now cranking a 318 cube Dodge Poly.
The best battery I can afford that fits in the space I have to put it in. sixty plus years of car guy stuff says that the one place you don't skimp is on the battery you run in your older car.
Don't know your setup, but I'm using 2 Optima 6v in series under my seat. They're on their side but since they're AGMs it's not a problem. Plenty of cranking amps!
Here is a picture of my avatar '38 Chevy Master Coupe battery located in the passenger side wheel well. The mounting bracked is attached to the frame. It is a bitch to hook up a battery charger but it works. When the wheels are straight, you can't see it.
Love it , I have built three family hot rods with battery exactly like yours under the front mudguard had no issues first one was a 38 Chev second a 36 Chev tourer third and current is a 46 Ford delivery , if you need to change the battery just jack it up and take the front wheel off .
The battery box in my A sedan is 0.75"x 0.75" angle, sized for an Odyssey 680. It fits under the rear passenger floorboard. Frame tabs are 1.5" x 1.5" angle. The master power cutoff switch is under the passenger seat, out of sight but within easy reach of the driver.
I have an Odyssey PC 925 mounted under the dash in my 31 coupe, no probs starting my sbc, been there 4 years now. Will not hesitate to buy again, Glen
I had this idle thought: https://www.jalopyjournal.com/forum/threads/battery-size-question.1306476/#post-15069252
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