It's a R 3509, and as Capgun says was a Wildcat. The frame is exactly the same dimension as the other HPE Muskin 400 series frames. However the steering neck is kicked out a bit, the axle supports are larger, and there is a hoop added to the rear of the frame.
The front end length is halfway between the Cat Hustler and the Eliminator, but the fork springs are the same. The 10" rims it uses are the same for the other Cat bikes of that size, and the virtually the same as the Rupp rims. They came with an H35 Tecumseh.
Your bike appears to have things welded on, an extra goose neck, and the forks appear to be remade, or repurposed off of another bike. Your handle bars appear to be the originals, but hard to be exact in that photo.
I have an original one which I will be restoring for the second time, only more completely with a repaint. The parts required to finish your bike as original are far beyond the price of sanity. Long chain guard, new front end, fenders...wheels. (Sorry) Not a lot of value there. I do have a fiberglass long chain guard that sucks, and a front fender for this bike that is rough. I could also take some measurements for any part of the bike if you need.
Or, you could drive here and have a field day measuring up what I have, and leave with any crappy parts I would toss in.