they'll fit but the forward/back handle is on the wrong side, can still pull the pin across wi ya finger tho, not like you move em that often. If its a later cab the foam, fabric and upper seat back from pre-90 MK2 seats will fit on the MK1 frames, provided they're the sports seats with the bolsters.
You can sometimes swap the handles over on the bases, providing the height adjust mechanism isnt in the way!