The last of Sal Trapani's ghosts on Mod Wheels at Gold Key (after Jack Abel and Charles Nicholas) was Jack Keller. He pencilled both stories in issue 6 (June/1972) with Trapani's inks. Again, with no credits, everything was ghosted here as far as the readers were concerned; but Charlton artists Nicholas and Keller didn't do anything else for Gold Key that I've found, so I'm betting Trapani subcontracted the pencils as he did elsewhere, unknown to the editors.
Here's a panel pencilled and inked by Keller from "Showdown at Horseshoe Flats" in Kid Colt 74 (July/57). Kid Colt is probably Jack Keller's best-known work; he drew the strip for about fourteen years at Atlas/Marvel. But his next-best is a similarly long-lived body of hot rod comics at Charlton, to my mind his connection to Sal Trapani. He also appeared in DC's short-lived Hot Wheels, with hot rod filler pages. Coincidentally, one Hot Wheels story was written by Mod Wheels' Len Wein.