I have a set of good 1.6 Mk1 seats to fit to a 1.8. The drawback is, normally to fit 1.6 seats to a 1.8, you also need to fit 1.6 seatbelt latches, not only having to get the latches but also cutting the carpet.
Mk1 1.8 seats in good condition are harder to find because [a] there are less of them than 89-93 seats [b] there are 3 different styles of 93-97 seats [c] The flame retardant upholstery has rubbish wear properties, even though it looks similar to earlier models.
I haven’t seen any writeups of swappinjg a 1.8 seat pan onto at 1.6 seat.
Why the pans; this is the main difference in the seats. The 1.8 has a welded on tab for the seatbelt latch. This is the difference between a 1991 seat and a 1996 JDM seat.
Underneath, the later seat pan has more drilled holes.
To remove the pans, its just a matter of splitting the seats, and removing all the hog rings from the underside
Looking at the bare pans, there is also another difference; on the later models, a bracket is added that appears to add some thigh support
The later seat foam has some additional cutouts
compared to the earlier one
Just roughly cut out the foam. The cutout around the seatbelt bracket doesn’t need to be much; the foam here is quite thing, and its easy to expose a spring.
Refit the pan, and secure the upholstery; I used cable ties, but you can reuse the hogrings
Start at the rear, so you can pull the front of the cover taut
With the cover fitted, make slits on the seat to expose the 3 captive nuts
Note, on the later cars, the upholstery is secured to the extra side bar, I didn’t see the need
Here is another reason to swap pans:
In some cases, the pan has been known to completely rot out. Once the pan rots, the seat loses integrity. If the pan is rusty, the foam can stick, so you need to ease it out, to avoid tearing the foam