The horsepower output of a 350 engine bored 0.030 inches over depends on various factors such as the specific components, modifications, and tuning. It is difficult to provide an exact figure without additional information. However, a rough estimate for a well-built 350 engine with that level of bore increase could be in the range of 300 to 400 horsepower. This assumes the use of performance components, proper tuning, and other supporting modifications. Keep in mind that these figures are general estimates and the actual horsepower output can vary significantly based on the specific setup and application.