hi
all mk2 seats will fit the mk1 as boyth are 19 inches wide on the runners
mk3 seats are 21 inches wide on the runners so wont fit unless you cut & weld em
on some mk3 seats you can swap the bases over using teh mk3 foam & covering onto the mk1 / mk2 seat base to fit
i did that before with an ibiza gti 16v seats into my mk2
danny