I have a 1970 Duster (originally a slant six) that will be upgraded to a 340 with a 727 trans and 8 3/4 rear axle (possibly 3.91 gear). A majority of the time, the Duster will be driven on the street to shows/cruises (maybe strip at Mopar events).

What type of rear leaf springs would you install on the vehicle? OE Leaf Springs: P4510268 and P4510269 or Competition Leaf Springs - Super Stock: P3412002 and P3412003?

With regard to the front torsion bars:
P5249148 - Torsion Bar, 0.810" Diameter for A-Body
P5249150 - Torsion Bar, 0.890" Diameter for A-Body
P5249151 - Torsion Bar, 0.920" Diameter for A-Body

*If vehicle was used more for drag racing (with a stroker 340 kit), what would be your recommendations?

Thank you in advance for your feedback!

I'd probably put on .920" torsion bars up front. As far as the springs, SS. Especially if you're going to use the car for drag racing Hopefully, other members would chime in to give more input.

I would run the biggest torsion bars you can get, something like a 1.06 because if you ever decide that you want something besides skinny tires it will handle better especially driving to events. Rear leafs, XHDs same leaf pack on both sides. Adjustable shocks....Tim

torsion bar wise for the street the .920 will be a huge improvement over stock. but i'd go as big as i could.. even the 1" are on the soft side in my opinion..

for the track only put the smallest in it.. slant six size.

for rear springs i'd call pete at http://www.bergmanautocraft.com/ and get him to set ya up with a set of the eaton springs he sells..

I daily drive my '73 Dart with 17" wheels, 1" bars, Hellwig front swaybar, 2 added leafs in the springpacks and adjustable shocks all around.

IMO, A-body Mopars should've gotten 1" bars from the factory.
Watching other cars on the road handle speedbumps and corners I say my Dart has pretty much the same handling characteristics as a modern day sedan.

For the T bars, anything from .92 to 1.00. Beyond 1.00 is likely a little much for actual street driving. The shocks and bars need to be matched up to get a nice result. The .92 bars would probably be happy with good parts store gas shocks. The 1.00 bars need a high end shock like Koni or Bilstein to control them. If you do not currently have a sway bar, now is the time to add one. At least the stock size bar, preferably bigger.

The XHD rear springs with their moderately higher rate would be a nice complement. Since the MP version (which I have on an E) tend to sag, may be worth trying the Eaton made springs mentioned in a previous post.

What size tires are you planning to use? For rear springs I recommend Espo springs. http://www.springsnthings.com/. I put the 1 inch over stock height rear springs on my Road Runner. Big improvement over the MP super stock springs I had on there before. The car rides much better and it hooks great at the track.

PST's 1.03 Bars and their G-Max springs, great combo for a street car. Adjustable front shocks that you can dial back for the drag strip week-ends.

I've been using SS springs on the street for 2+ decades. Wouldn't change a thing for your application. Fronts for crusing and fun with an A body I'd go with no bigger than .920 but no less than .880

Damon

/6 bars for a dragger. for street/dd I had a 65 dart SB with SS 003/003 springs (came that way as a roller) & thick circle track t bars & it rode high and tight (I loved it), wouldn't change a thing