It's a 70 frame and wheels, but the handlebars look more like the 71. The engine is also a 71 and up engine (big decal wasn't used in 70). The clutch guard and rear sprocket isn't original to any year Rupp as far as I know. The grips and peg covers aren't original to Rupps either. I'd say it's a mash up of a few different bikes.
It's definitely not a Black Widow, but it could be the engine off of one. I even doubt that. The muffler looks like one from a Garden Tiller. Maybe they swapped the shroud over ?
Outside of the engine, there isn't much value there. I'd be very leary of this basket case of a bike