The factory rating was 275 through 1971 but the 340-6bbl T/A & AAR was 290. It's common knowledge that they were very conservative numbers. In 1972 the 340 lost compression and went to smaller intake valves. The factory started using a "net" rating which was advertised at 240. The '74 360 was rated at 245 which had the 340 cam, springs & heads, 20 more cubic inches and a bigger Thermoquad. Still debatable ratings for both.
