I think I'd go in the archives and copy hotroddave's "super duper gas mileage 318" build and toss that in there...high compression, tight quench, very short solid cam and a t-quad...
1976 Spinnaker White Plymouth Duster, /6 A833OD 1986 Silver/Twilight Blue Chrysler 5th Ave HotRod **SOLD!*** 2011 Toxic Orange Dodge Charger R/T 2017 Grand Cherokee Overland 2014 Jeep Cherokee Latitude (holy crap, my daughter is driving)