Have you measured the bottom of the Sears battery at the store?
I pulled up a picture of the battery and it looks beveled at the bottom. I can't tell if it's beveled enough to fit.
I've used AutoZone batteries for many years.
AutoZone has a 27F on its website with the right dimensions:
It should fit but I'm sure they'll take it back if it doesn't. Make sure you ask about that, though.