Winnebago only used a Dodge or Ford chasssis in 1970. If you have a Dodge chassis:
The regulator is mounted on the plate mounted to the rear of the engine above the bell housing.
If you need more information please refer to the Description and Troubleshooting information under the Charging section of my website: http://dave78chieftain.zxq.net/
Ignore any electronic ignition references as Dodge did not implement that until 1973.
If you have the Ford chassis, I would have to dig deeper as I have never looked at that.