All "FE" series engines have 352 cast into the blocks, unfortunately. Keep in mind that a 352ci has the same Stroke (3.500) as a 360ci and a 361ci engine, but different Bore sizes. To determine if your 352ci is a 352ci or something else, do this.
Remove the #1 spark plug. Manually turn the crank to the point where piston #1 is at dead-bottom to the top edge of the cylinder wall. Measure the depth of the cylinder with a rod, stick, or ruler. Measure the distance between the piston dead-bottom to the top edge of the cylinder wall. If the stroke measures 3.500" you have a 352ci engine. If it measures 3.784" you have a 390ci engine. Or a 391ci, or 406ci, who have different Bore sizes, but the same Stroke measurements. See the chart above.