This is what I did in my thread on "Cheap 318 Power" that took the car from a /6 to a 318 of a '79 vintage which has less comprssion than the earlier engines. Most Dusters will run in the hi 16's to low 17's with a 318 and a peg leg hwy geared rear.
I added the following parts from top to bottom;
MP unsilenced air cleaner , though any open element will do. I have had this air clener since they were like $50, but we'll just use that as a base price for other cleaners.... $50
A Holley 1850 carb rated @ 600 cfm. It's a 4160 model that I convertered to a 4150. The carb did use a rebuild kit and the carb itself was $20. Rebuilf kit $42. So for basicly under a hundred bucks, I have a excellent carb.
$100 (Total $150)
Intake is a LD4B picked up cheap. Otherwise a Edelbrock Performer should be used.I picked up this used unit for a bout $50. Glass beeded it myself. ($200 total)
Crane Cams split duration @ 216/228 -.454/.480 lift Comp Cams, Huges or Lunati has excellent vesrions of this cam and are probably better to use.
Hooker Comp. headers coupled with a Jegs/Sumitt true dual exhaust kit @ 2-1/2. I picked up the cam/lifter and spring kit since matching springs is a must.
( $185 for cam, springs will run about another $70 or so. Total so far, $455)
And electric fan and lokar cables were nice extra's as was the B&M floor shifter. Though not needed, how likes a column shift hot rod?
B&M floor shifter; $120
Lokar cables, expensive but you don't need them.
Permacool E-fan; I for get what I paid, but it'll run around a $150 or so with thermostat kit for a on and off by itself fan.
We'll just add the floor shifter to this expense.
Ruffly speaking. Without shipping that is. Total $575
I did swap out the 7-1/4 rea for a 8-1/4 rear that is sure grip equiped w/3.21 gears. Great deal @ $200, no brakes or backing plates which suited me fine since I had a Cordoba donte it's 11 inch brakes. Backing plates swapped right over and everything works great.
This car can run high 14's. The one and only time at the track on a cold day, I did run it ruffly tuned to a 15.14 @ 89 mph. Ruff carb tune, ruff distributor tune, spinning out of the hole on skinny stock tires .... I know I can whittle down that .14 for a 14 second and quicker run.
Lookie here;
http://www.forabodiesonly.com/mopar/showthread.php?t=10508
A serious help in this would be a high stall converter and rear gear as well as milled and preped heads with better valves.