The holes might be offset but is the firewall offset? If the firewall is straight, you can shim the mounts to get the offset. You can measure the distance from the back of the mounts to the thrust washer. Use that as the radius of a circle and calculate about 3deg. of offset. That 3deg distance is the offset to the right from the centerline(as you look at the firewall). It should put the thrust washer back on the center. Other folks put the engine on the centerline and use the rudder to correct the left pull.