Holly used to, about 45 years ago, offer a spread bore model as a direct replacement for Quadrajets. I had one and it worked beutifully. It was a 650 cfm as I recall and fuel economy just about doubled on a '70 model 300 hp 350.
Good Luck with your truck!
Rick
I had the exact opposite results when I tried one of those carbs on my '68 El Camino with the L79 327" (350 hp). It greatly decreased the performance because the Q-Jet was 750 cfm and Holley was 650 cfm. Highway gas mileage with the Q-Jet was 20 mpg verses 14 mpg with the Holley.
