943's are a good spring in the right application. i run a roller in the 270's@050 with 650 lift & they've lasted 3 seasons reving to 7300 before we detected valve bounce on a set of -1 indys. when i stepped up the cam with 280's@050 those springs didn't last as long. by the end of the first season we were detecting valve bounce so we had to step up the springs. they're easy on the rocker gear, even Indy's ali cheapies.