No prob, free advice is usually worth what you pay for it!!
If most of your "fun" on the street is focused on straight-line, then I wouldn't sweat the ball joint length at all, particularly if your drop is as mild as it is.
Yes, you can certainly add a bump-steer kit with the GT500 arms if you wish! Remember that bump-steer is a change in toe angle during vertical suspension motion. This toe delta is created by differing arcs between the control arm and the tie-rod, usually measured over a +/- 2" range of motion. When you add the taller ball joint, you are effectively lowering the outboard end of the control arm, changing the relationship between it and the stock-height tie rod pretty dramatically. This is what creates bump-steer issues with the X5-type ball joints. Ford's OE design actually has very little bump-steer, going out all the way to the extremes of being on the bump-stops, and at full droop. A bump-steer kit neither fixes nor creates a bump steer issue, it merely allows us to tune out any that may exist. Whiteline's kit is the only ball/socket setup I've seen, and it's tuning is preset to work with their extended balljoint, effectively bringing the entire front geometry right back to stock. All the others, Steeda, Maximum Motorsports, etc., all use a tapered stud in the knuckle, with a threaded bottom portion that allow you to move a ROD END up and down via a series of spacers. This is where the tunability comes from. I put ROD END in caps, because rod ends (Heim joint) and streets are not generally a friendly mix. The inner race is exposed to the elements, road salt eats the teflon lubricating band, they wear faster by a factor of at least 10, and they require fairly regular maintenance. If you were dissapointed by your stock ball joints "only" lasting 70,xxx miles, then you will be hating life with a rod end that will probably show play after 10,000, if not sooner.
Also, treat the front and rear suspensions independently. Unless you want to get into cutting up the tub of the car, there's no way to raise the front of the rear LCA, the only option is to lower the rear. Also, be careful with your bushing material choice when looking at any suspension component. Harder, stiffer bushings (rubber softest, poly in the middle, Delrin or Heims the hardest) will reduce bushing compliance (flex, or distortion) which makes them more precise, yes, but there is a downside as well. The lower the compliance, the more transmitted vibration. On a race car, with all Delrin or Heims, when you roll over a penny in the paddock, you not only know you rolled over it, but you can tell what year it is, and whether it came from the Denver or San Francico mint. Awesome, right? Until that same car hits a pothole, and all but breaks your wrist because none of the shock was absorbed by the bushing. Also, with a race setup, all those little noises (which ARE vibrations!) will be transmitted DIRECTLY into the car. Rear gear, trans, exhaust drone, tire road noise; all of it will become immediately apparent, and obtrusive. If you're looking for "crisp" handling, that's one thing, but if you're primarily a cruiser (which I would bet on, based on your mileage), then all those noises and vibrations can get extremely annoying.
