I have replaced the pinto with a silvertop 2.0L zetec in my car. I get an engine vibration at 2900-3300 rpm sufficient to have fatigue cracked one alternator mount and to loosen various bolts round the car. Currently using hard rubber mounts from westfield for engine and box which hold the engine fairly rigid.
Any other zetec owners found similar experiences and anyone have any ideas how to reduce or stop it?

Changing the mounts would probably help.

Are you sure the engine is not touching the chassis anywhere?
I had this problem in a striker and that was the cause.