According to Hydrastar, their # HS481-8067 vented Electric Over Hydraulic Actuator system does indeed include a charger for the battery used by the break away system. The charger would connect to the 12-volt trailer connector feed from the tow vehicle.
Since your # 90885 Tekonsha Prodigy P2 brake controller is EOH actuator compatible, you won't need to use the adapter module that's included with the kit.
I've linked to the installation instructions as well as to a product description... view full answer...
The Timbren helper springs # TGMFK15A is a complete axle kit so you get 2 springs, one for each side of the axle. I have included a link to the installation instructions for you and a link to a help article on Timbren systems. view full answer...
I spoke with my contact at Lippert and he said that Lippert Components HD 6500-lbTuson 5th Wheel RV Landing Gear Motor # LC196308, is the motor only. For the replacement gearbox you will want # LG-179015. view full answer...
The Timbren Rear Suspension Enhancement System # TGMRG25C comes with 2 jounce springs for your 2004 Chevy Avalanche 1500. It will give you the upgraded suspension for both sides of your rear axle and each side works independently to compensate for off center loads and reducing body roll around corners. I've attached a couple videos to assist. view full answer...
I went out to our warehouse and took a picture for you of the brake shoes. The 12" x 2" Hydraulic Trailer Brake Shoe and Lining (One Wheel) # BP04-160 look like the attached picture. They have the same internal bracket you see but have 2 additional holes leaving the other holes in the locations that you referenced. view full answer...