There are several different ways to remove Briggs flywheels, depending on the model. We need the Model, Type and Code information, which should be stamped on the side of the cooling air cowl above and forward from the intake port, at the tip of the yellow arrow:
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You may need to polish up the cowl in that region. The tractor seems to have been made in the early 1970s, unless it is a 990A, which would make it even later. By then, all Briggs engines had the required information stamped on their cowls.