I think the only way is to store the styles you want, remove them all and then set them again.
$('.selector').each(function() {
var keepStyle, $el;
$el = $(this);
keepStyle = {
font-weight: $el.css('font-weight'),
font-style : $el.css('font-style')
};
$el.removeAttr('style')
.css(keepStyle);
})