How do I get the absolute best MPG

[mcmullinauctions]

Hi.
I am an insurance agent and I drive ALOT. Sometimes 2000 miles a month. I want to replace my 2005 chevy 2wd extended cab (5.3 /auto) with my 1963 when it is finished. I want to get the 18-19 mpg I currently get or even better....HOW? I am not worried about taking off fast or performance (within reason). I just want to use the 63 factor body, frame, and upgrade the drivetrain and suspension. I would love to stick with a 4 or 5 speed and have a v8. I am not opposed to a 700r4 though. Whats the best way to do it. TPI? 5.3 swap (can I run a t-5 with that?), TBI injection? I just want to run 70 on the highway at around 1800-1900 rpm. What's you opinion? I'm trying to do the drivetrain without spending a rediculous amount of money too. Thanks