Well the kdx even stock, (and this is the newer models) is only 36 inches on the seat height, so you are only looking at a difference of two inches. If you have to, use the lowering links, but I wouldn't shave the foam on the seat, I don't think it'll be needed, and the newer kdx's don't have much seat cushion to spare. I didn't look up the specs on the older 89 through 94 bikes, but I bet they are lower than 36 already.
73 cr250m elsinore, 85 atc70, 85 250r flattracker, 87 250es bigred, 86 tecate, 2004 gas gas de300