A well tuned carb. in an old V8 will run fine.
My 1983 Jamboree is build on an E350 with Holley based carb. It wouldn't pass smog (Ca.), so I had the carb rebuilt with a modern kit (alcohol resistant parts) and put fresh gaskets on the EGR plate/riser/carb. It passed smog with flying colors.
The ignition system is made better by adding an adjustable advance module. I wouldn't buy an HEI distrib. Once you have rebuilt the carb. and added the adjustable advacer, it will run great!
You really don't get any better mileage with EFI conversions on older engines because you aren't altering compression. I would not be afraid of another carbureted motorhome.
Jose