If you are setting in the pilots seat, the engine should be angled to the right one or two degrees and angled down by the same amount.

If the engine mount were mounted in the center of the firewall, the crankshaft would be too far to the right and too low in the cowl.

Therefore the engine mount must be shifted to the left when setting in the pilots seat and up so the prop hub will be at the center of the cowl.

You will have to reverse engineer the plane. A guess would be in the order of 1/8" from center on the firewall.