Just got done with a 1969 Rupp Roadster. It's not an accurate restoration, but it's what i could afford to do. When i got it there was no motor and missing a ton of parts. These Rupps make you poor buying stuff for them!
The motor is a lightning coil Tecumseh HS50, instead of the stock H50. I could not find a lightning coil for an H50, so instead I installed an HS50 (and put an old style 1960s logo on the motor.) It actually worked out quite well doing this. It has the 2speed transmission. Also a Dellorto carb. The exhaust I made myself. I could not afford an original exhaust for this bike, man they are expensive! Also the exhaust/intake ports for the HS50 are on different sides of the motor, so the original exhaust probably would not have worked anyway. The custom exhaust cost me next to nothing to make, and it looks OK enough for my needs. Made all the decals myself too. And a weld-on kickstand (originals too expensive.)