Have never heard of JC Whitney nor Dorman, let alone having anything to do w/Leafs. Are there any actual specs on that thing? I doubt it's the right voltage and capacity.
As LB said, JC Whitney used to be the king of mail-order auto parts, I used to order from them all the time, everything from Rings or crankshaft bearings to cheap Chinese made plastic auto flashlights and auto accessories.
Dorman is probably the largest current supplier of aftermarket auto parts. Cheaper than OEM in both price and quality, overall I've had pretty good luck with their parts. My most recent purchase, a rubber hatch release button for our Prius. The old one turned into a sticky goo, making your fingers sticky or black everytime you'd open the hatch. The new Dorman installed like a Breeze, lets see how long it lasts.......the OEM lasted a little shy of 10 years.
Not sure I'd trust ordering a replacement battery from JC Whitney or Dorman, probably best to stick with OEM or a junkyard for something like that