Many Epson projectors will allow you to change the Image Type to present to a 4:3 / 16:9/ or 16:10 Image. To do this you would want to first set the image type from within your projector settings
Then you can select a 4:3 Resolution to display to.
If you projector does not offer this option it is very possible that it only presents to one type or image, either 4:3 or 16:9 - Please consult the owners manual to identify which one if this is the case. Alternately, you may search the model type online to identify the preset aspect ration.