Cruise friendly low 12's with a 340 Dart

Hey Everyone, after years of bracket racing my dart, I'm doing more cruising and car shows now so my goal is a pump gas cruiser that runs low 12's.

Here's my current setup

71 Dart Swinger
73 340 cast crank engine
stock J heads
clutch fan and 180 Tstat
stock 340 manifold
Weind action plus 8007 dual plane intake
Purple shaft 284/484 cam
Holley 3310 750 (70 primaries #5 powervalve, 10" vacuum at 750rpm)

727, 8 3/4, 3.23 suregrip 489 case
GER 11" converter 1500 stall/1800 flash (i don't like it),
BFG drag radials

Anyway, the car runs 13.9-14.0 and gets 10-12mpg. i would like to run low 12's and get 15-16mpg with a more cruise friendly converter.

So far, i figure i need headers (TTI or Dougs), a different converter (suggestions welcomed), and maybe the Eddy 850 carb with the small primaries and giant secondaries.

I wanna keep the 3.23's for cruising BTW.