The original holes placed the engine off center for a reason if there was the usual thrust setup. Most models have downthrust and right thrust. When the model has those and a cowl, the motor mount will be moved around on the firewall so the spinner will be centered in that cowl.

They sometimes make a mistake on the location, but not often.

To very roughly verify the location, look at your firewall from the side and top. If it's got downthrust and right thrust the center of the motor mount holes will be moved left and up from the center of the firewall. You can more accurately verify by tack gluing the engine/motormount on the firewall. Temporarily place the cowl and look to see where the prop shaft comes out. Needless to say, you want it centered in the front of the cowl.