The dual sparkplugs of a 5.7 V8 are such an advantage that engine should be the starting point.
(Since even the late dual sparkplug 4.7 have bad reputations I will not consider those.)
An air to fuel ratio of more than 20, perhaps even 25 can gain a lot, and you “probably” need fuel injection to keep all 8 cylinders even.
Dodge Ram, or maybe Dodge Magnum station wagon?
Better aero of Magnum would help a lot.
The magnum head chamber is very efficient when set up with quench and doesn't need the help of a dual plug deal like the hemi chamber does to get a complete burn.
