Why the fook would you wanna put 18's on a Mk3? 16's are more than enough, 17's can look good.. but 18's? Seriously

No, Mk4 seats will not fit, unless you weld the correct mounts onto the floorpan iirc
Not sure how much work is involved fitting a Mk4 steering wheel but I think it is quite a tricky job, try and track one down from a 3.5 cabby
