MKII seats are a good replacement for the worn out seats in your MKI. The styling and colors are similar and they fit just fine. MKII turbo seats have the same adjustments as the MKI seats, whereas the MKII NA seats only offer height adjustment for the front of the seat bottom.
To install the seats, the mount feet must be cut off both pairs of seats. The mount feet are spot welded and affixed with a heavy duty rivet. I find it easiest to grind the heads off the rivets and drill the spot welds out. Be careful with the feet from the MKI seats you will use these on the new seats.
Both front and LH rear MKI feet will line up with the floor mounts when they are mounted to the MKII seat rails in the original MKII feet locations. The RH rear mount foot will have to be moved slightly on the rail to line up with the floor mount hole.
I bolted the front and LH rear MKI feet to the MKII rails and had them welded in place. Then temp installed the seats and lined up the remaining mount and temp welded it in the proper location. I removed the seats and then thoroughly welded the feet to the rail.