The hubs are probably Normandy. They say Schwinn approved, but Shwinn didn't make hubs. Weinmann rims and brakes were pretty standard. Those bar end shifters will give you a very slow shift because of the cable length and housing compressibility. The bare-metal housing is original with those shifters, but you'll get a quicker shift if you replace it with modern non-compressible derailleur housing, or switch to downtube shifters. (If you want to get rid of the the bar-ends, I'd buy them. I had a set just like that in 1976, and I've got an older bike I'd put them on.)

BTW, you really need to replace ALL the grease in the bearings of this bike: hubs, bottom bracket, and headset. Old grease becomes hard and very non-grease-like.