The AGM design appeals to me, but I didn't win the lottery and I've been spending too much on other things lately. :/
I'll call AutoZone, but I'm betting they'll tell me if the car starts they won't prorate my battery (it's 5 months past the free replacement warranty).
Also, according to their website, the 65-DLG is NLA online and in stores (probably discontinued for good reasons!), and I suspect they'd try to upsell me their Platinum (AGM) model.
The Motorcraft BXT65-850 is $156.99 at the local O'Reilly stores plus $18 core.
Even if O'Reilly will refund an AutoZone DG core, it could be moot if my model is discontinued, since the manufacturer won't want it back. I wonder whether AZ is obligated to refund the core on their own house brand batteries, even on discontinued models.
If O'Reilly won't refund the core but AZ will, then the Optima for $227.99 at AZ is looking better.
If O'Reilly will refund the AZ core, their price on the Optima red ($215.99) would be the better deal on that battery – it would be $6 more than AZ's total price if they don't refund the AZ core but AZ did refund it.
I imagine they might just refund an AZ core, even if policy dictated otherwise, if not doing so meant losing a sale to their competitor, but who knows...
I'm assuming the required group 65 adapters still come with the Optima (I've read they're supposed to) or will be sent free of charge via Optima support. If I would need to purchase those, that could break the deal on the Optima, depending on how much they cost.
The Motorcraft BXT65-850 has 850 CCA vs. the Optima's 800, but 800 should still be overkill in south Texas.
I don't recall what model battery came with my new 4.6L Bird back in '96 – I may or may not be able to find that info in old documents I have from the sale – but I'm guessing it was the 650 CCA version, and it seemed to work fine.
I did some additional shopping for AGM's while I was at it:
AutoZone Duralast Platinum (65-AGM) has a 3-yr warranty w/no prorate, 750 CCA (or 775, depending on where on their site you look) and costs $191.99 w/$18 core.
O'Reilly Super Start Platinum AGM (65PLT) has a 3-yr warranty w/no prorate, 750 CCA and is $174.99 w/$18 core.
Advance Auto AutoCraft (65-AGM) has a 3-yr warranty w/prorate, 750 CCA and is $178.99 w/$20 core.
Sears DieHard AGM (50765) has a 3-yr warranty w/prorate, 775 CCA and is $176.99 w/no mention of core on their website.
Interstate AGM (MT7-65) has a longer warranty at 4 years (proratable?), 770 CCA and MSRP of $273.95-$303.95 (I couldn't find it locally).
NAPA Legend Premium AGM (BAT 9865) has a measly 2-yr warranty w/prorate (a whopping 18 months on their non-AGM Legend batteries), 750 CCA and is $194 w/$18 core.
I reckon 750-775 CCA and 140-150 min. reserve would be adequate for me, but then "you get what you pay" is probably in effect with those less costly units in terms of reliability.
According to the Optima warranty pdf, they don't prorate their products, and now apparently neither does AZ prorate their own. So, I'm looking at a max 3-year coverage on any battery purchase from AZ, whereas the flooded Motorcraft prorates to 100 months at O'Reilly.
I'm still on the fence about splurging for an AGM. I'll let y'all know the particulars after I contact the various suppliers regarding core refunds – that $18-20 could make or break a sale I guess.