The cowl is different AND the older seat has the "cubby-hole" built into the seat whereas the later seat has a cubby that bolts to the subframe so you'll need that too.
I've found the original cowl and by eye I don't think the later "cubby hole" will fit . I will take mine off and determine one way or another once the seat arrives.
The good news is that if I do buy the later "cubby hole" they are available at almost reasonable prices. Might shout her a new too tray while I'm at it as the original is a bit knocked about.
What brought this on was that in the 1980s our State introduced cheaper single-seat vehicle registration. In order to qualify you had to permanently remove the rear foot pegs and shorten the seat to less that 500mm effective length.
At the time the seat base was well rusted so we fitted a K100 "police" seat (same base at G/S single seat but with black covering - and half the price) and a G/S rear utility rack.
Roll forward to 2017 and the single seat rules have changed so that all that is really needed is to remove the rear foot pegs.