[BR3W CITY]

~380rwhp/~450chp w/ my heavy 4l80e,12bolt, and 15x12 rears w/drag radials (yay rolling resistance lol)

In my 66 I get about 13-15city and 17-20 on the freeway. This is also with a slightly wonky convertor/od setup right now, so I'm on the lower end of that spectrum, but I have seen the 19-21 in ideal conditions with smaller rear tires.

You cant do much for aero on these trucks, aside from getting them lowered a tad and putting hard, narrow tires on (which sucks, so don't actually do that). Your best bet is to lose weight in the truck, its the next best thing for mpg and pwr/lb