As Jim said, they're necessary for the smog tests (if you're in an area that has them, or might try to sell the rig into such an area).
My '85 Ford 460 also had two smog pumps and all the related junk. I took them off and stashed them away in the attic. My local auto parts store had steel plugs specifically to plug the holes in the manifolds. I also disabled the exhaust gas recirculation valve and plugged off any dangling vacuum lines.
The changes had a mildly benficial effect on drivability, but gas mileage didn't improve. My next step would have been to find a pre-smog (like 80 or earlier) caburator. I had heard from a friend at Ford that the mid 80's and later engines were deliberately jetted rich to give the afterburners enough unburned fuel to work with. I understood that GM did similar things with their big engines. These were the chewing gum and bailing wire attampts to avoid the cost of going to electronic engine management.
We decided that we hated the floorplan so much after a season and a half that we unloaded it through a consignment dealer, so I never tried the replacement carb. I left all the smog gear in a box in a cargo bay. Never heard from the buyer.
Frank Damp -Anacortes, WA,(DW- Eileen)
ex-pat Brits (1968) and now ex-RVers, as of 08 Dec 14.