Is there a specific size inner tube, other than 16', required for the Drifter 1500 front and rear tire? Is a rubber strip required for the rim? Are there any recommendations for the 90 degree valve stem angled rear inner tube?
You should match the tube to the tire. Wherever you get the tires ask for the tubes. If you have the tire off the bike, you can check the tube markings. A tube usually will work with a couple of different size tires and may be labeled with those sizes. There are Kaw part numbers for our tubes and they are still available through parts dealers last time I looked. The same size tube may work for front and rear tires.
Rim strips are needed due to the spoked wheels. Rear tire really needs a 90, front not so much.
Yes, there is a rim strip, and the front tube requires a metal center valve, the rear uses a 90° metal valve. The front wheel is 3" in width, and the rear is 3 1/2" wide. The front tire is a 130/90-16, and the rear is a 150/80-16