vibration question
 

My 88 vert has had a vibration since I bought it and I'd like some opinions on the possible cause. With the car not moving I'm getting vibes in the 2500-3500 rpm range.It doesn't change when I depress the clutch. I've installed a different engine that I know is fine with the same result. The previous owner claims the clutch was replaced before I bought it. It appeared new so it's still in use. I'm now wondering if it may be causing the vibration. any opinions? Thanks

Check your engine and transmission mounts

did that

Could have the wrong series flywheel installed on the engine. S4 flywheel with S5 engine etc.

I changed flywheels with the engine. I also disconnected accessories like ac and power steering pumps, cooling fan air pump and cooling fan with no change. This one's got me chasing my tail.

Does anyone else have any ideas about my vibration question?