46re trans build parts selection help please

The kickdown band you want to use is the Raybestos Pro Series. Used to sell lots of these to a High Performance Diesel shop.
Be VERY VERY Cautious if you're going to take the overdrive section apart. The overdrive clutch spring is compressed, and unless you've got the PROPER tool you can do yourself a lot of harm when you start to take the OD apart. Transgo makes a good replacement spring.

For all your needs for HP/HD Diesel parts or any make transmission items you might want to check out www.tcsproducts.com . They manufacture just about everything you will need for your automatic transmission needs. They also manufacture the tool to take the OD section apart. You can phone them 1-800-960-1177, ask for Paul. Good guy and really knowledgeable. If you think they are too far away from you to deal with, ask Paul who their distributor is in your area.