360 engine vibration at ~3000rpm

If that is a Performer RPM intake, then the standard Performer would probably give better tq at lower rpms-with no loss at the top end. RPM is designed for 1500-6500 rpm range. Your engine is peaking at 5200. Perf rpm range is idle to 5500. With your greater cubes, that upper limit will be slightly lower than 5500 & should be close to ideal with your 5200 hp peak.