No not a common issue but sometimes they become spongy .The ones I have found that way were oil soaked too.I don't know if the oil caused it but maybe.
Yes, oil does in time tend to attack the elastomer material and this includes some of the urethane mounts (import material more so) also.
As far as the clearance problem particularly that with the FE mounted in this chassis, in order to resolve the issue of attachments mounted to the cylinder head coming into contact with the shock tower(s), if only one side, the engine may need to shifted or rocked over some, this accomplished by loosening the mounts, lifting one side and allowing the opposite to drop 'some' this tilting the engine away from the offending side and ending the unappreciated vibration imparted to the chassis. This effort may be stymied by a lack of movement available in the fixturing so slotting of the mount holes may be necessary. If the entire engine is just situated to low causing both sides to come into contact with the shock towers and or the cross member then shimming between the mount and engine block will aid here.
Scott.
