certain spindles require wheels larger than 15". with arms it doesnt matter so you could keep your 15" sport wheels. DJM spindles use stock ball joints so you can still get replacements. from what Ive read DJM 3" lowering lower control arms are not supposed to be used with lowering springs, your supposed to use stock springs. you may or may not need the uppers... with my 4 inch djm kit (2in drop springs and 2in drop lowers and uppers) you need to use the uppers to obtain the correct camber angle. without the uppers (on the 4inch kit) your camber will be off by 1 degree (I dont know if this is the same on a 3" arm). another selling point for control arms are that your wheels dont get pushed out like they do will belltech spindles. and like Sierra said before, if you ever bag your truck there is very little modification to the lowers. The spring basically sits in a cup, you could easily just set a bag in instead of a spring. so I guess I would say if you want to go lower than 3" static then pass on the 3" arms but if youll be happy with 3" then go for it because it is a good deal for those arms