I want to make my 4.8l truck bad?

go old school and build a carbed 350 to live in that truck....wait, that probbably wouldnt pass inspection where you live(it will here)...just get you a vortec 350 and be done with it....and 9 mpg? dammm...my 1986 suburban gets 15 and its all origional from carb to differential...and grandpas bad *** 1977 longbed c10 with a 350(cammed, 883 heads, edelbrock intake/carb, and hooker longtube headers) and no overdrive gets 12mpg