Having driven a few V-8 ZJ variants, I've noticed that the Chrysler 318 cid / 5.2L may offer some usable torque (300 lb-ft) in efficient low-speed operation. The rest is up to high-speed aero treatments.
The "Low-Hanging Fruit" advice generally applies: get rid of mud flaps, cargo/roof racks, and block the grille (if possible). More extreme measures include lowering, etc. Consider a second vehicle for commuting and the like.
Best FE to ya
RH77