the uprated rubber mounts that I got from humphris transfered a fair bit of vibration initially to the cabin but most of it is through the steering cos the rear engine mount is located right next to the steering rack. now its slightly softer but wedged a wooden piece in the rear mount to ensure its stiff.
god knows what a solid alloy engine mount will do or feel like. perhaps it'll be like sitting on a jack hammer all day. more likely to shake your body, hands, any car fasteners or windows to pieces.
for temporary racing, sure. but for long term distance travelling prob not advisable.
