I bought a set off of ebay. My 1998 has power mirrors and these replacements extend and have power. They come with an inside brace brkt and the vibrate a little. The factory mirrors on a 90 are the same as a 98, not big enough for a car forget about a truck towing an enclosed trailer.
http://www.ebay.com/itm/Towing-Power...c52c1f&vxp=mtr