Why is my new AC Delco replacement battery not fitting correctly?

[Brian E.]

My car is a 67 427 / 390 horse without air conditioning My car is a 67 Corvette 427 / 390 horse without air conditioning. The battery (and heat shield) sits on a welded steel battery tray that mounts on the passenger side frame rail. Near the bottom of the battery tray, the tray grips the battery on the front surface of the battery with an integrated hold down and on the rear surface of the battery with a separate hold down clamp.
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The battery that was in my car when I purchased (5 years ago) my car was a 24PG 88865263 (pictured below), which fit and functioned perfectly and has the following attributes:
• Correct terminal orientation,
• 700 CCA,
• indentations in both surfaces near the bottom of the battery for the battery tray hold downs,
• the 42 month replacement warranty,
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According to my AC Delco shop as well a separate GM dealership, X years ago the AC Delco 24PG 88865263 battery was replaced with 24GHR 88866250 which has all the same attributes except for one… Where the case for the older 24PG 88865263 has concave-shaped indentations for the battery tray hold downs, the case for the newer 24GHR 88866250 has large flanges (see pix below).
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These new flanges are bigger than what the original OEM battery tray hold downs can handle. After trying with all my might, I can get only the slightest edge of the flange under the front battery tray hold down and I’m worried that’s not enough. In case anyone is wondering, yes, the heat shield is installed correctly and is not interfering with the fitment.
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Is this a problem?
Will this battery be secure?
Has anyone else experienced this fitment problem?
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Thanks in advance for your help.

[Edward J.]

Brian,I have a 9 year old professional Delco Battery I put in my 63 that I had to modify, It has a handle to carry it easily, I used a cutting wheel to cut the mounts off the battery so the hold down would work. I think the batteries today are meant to work with alot of GM cars. From looking at you pick the are 3 raised ribs, maybe if you grind them down the battery will slip into the tray some to give you enough room? I also think if you go with lesser Delco battery 3 year warranty the configuration is different, my friend just brought a new Delco battery that did not have the handle like mine is.

[Brian E.]

I just got off the phone with AC Delco, and I'm not surprised that my call was a waste of time because the type of person I need to talk with is an AC Delco engineer who could tell me if those flanges are solid (or not). I don't mind cutting into a $150 battery and potentially ruining the battery. My bigger concern is what's inside the flanges... is there a cavity with battery acid inside the flange (not likely) or are the flanges 100% solid without battery acid inside them. Again, I'm not as concerned with ruining a battery as I am potentially weakening the ability for the battery case to absolutely (under all conditions and circumstances) contain the battery acid without pouring out onto my car's frame.