This is for a AD truck in the 47-53 range?
In Canada, either the Peavy Mart or Canadian Tire (group 1 size) 6 volt commercial battery is the correct size.
Dimensions: 9 L x 6.8 W x 8.75" H (22.8 x 17.2 x 22 cm)
That should be about 70-80 USD, ($103 CAD after core return).
In the US at O’reilly they usually have it in stock
Super Start Fleet & Heavy Duty Group Size 1 Top Post Battery
Part # 1J Line: SSB
$97 with a $15 core
-s