There is almost no way of installing an engine without some cutouts on this plane.... the cowl is narrow compared to the scale.

The least obtrusive would be to mount a rear carb engine perfectly vertical then use the pipe header for this plane.... you'll still have a slot cut out where the header comes out a bit... but no cutout on the right side of the cowl.

It's really not all that bad when cutout as designatedint he manual though.