I would go with a "fairbanks" servo. It's about 30 percent more holding power than a vette servo, and its billet. It's defiantly a "band saver".
http://www.rhino-transmission-parts.com/4l60e-problem-solvers/ it's the third one down. If it were me, I would find a local parts place and buy from them. I sell online, but I am a big fan of helping your local economy. If it's your first build, it will be good to get in with someone local in case you need a question answered or have to return a part. I can email you a book if you want, it will help get you started. Remember, have a clean clean work space, take your time, pay attention to detail. You can spend whatever you want on these. The weak points are the 3/4 clutches, you can put a "Z-pac" upgrade here, stock isn't bad though. Make sure you do change the 3/4 piston though. Sunshell, get a "beast". Band, get a good kevlar or high energy band. Servo, it applies the 3/4 band. Vette or fairbanks (more you spend here the better). Make sure the rear planet has no "play" in it. Be sure to line your pump up, and install at least a .500 boost valve in it. If it has plastic accumulators, be sure to replace them with aluminum. They are very cheap and the plastic are prone to crack and cause a clutch burnup.
