What's a "rwd vacuum"? On a Datsun 1200, the only one that can cause the RPMs to jump way up is the throttle opener on the carb. It's the big round thing on the top of the carb. Remove the hose and plug it.

If you don't have a Datsun 1200 engine, just go the library and view or checkout the book for the kind of car. You may need to drive to the regional library to find the right book. Nissan and Mitchell have vacuum diagrams, most other books do not.